The Stories Behind 20 Inventions That Changed the World

Brian Mueller (super soaker), New Africa (light bulb and seat belt), Feng Yu (duct ape), los_jan (toilet), non123 (Walkman), 3DMI (Hubble), Areeya_Ann (birth control pills) // Shutterstock; Julia Lemba (backgrounds) // iStock via Getty Images Plus
Brian Mueller (super soaker), New Africa (light bulb and seat belt), Feng Yu (duct ape), los_jan (toilet), non123 (Walkman), 3DMI (Hubble), Areeya_Ann (birth control pills) // Shutterstock; Julia Lemba (backgrounds) // iStock via Getty Images Plus / Brian Mueller (super soaker), New Africa (light bulb and seat belt), Feng Yu (duct ape), los_jan (toilet), non123 (Walkman), 3DMI (Hubble), Areeya_Ann (birth control pills) // Shutterstock; Julia Lemba (backgrounds) // iStock via Getty Images Plus

You might find it impossible to imagine a world without your smartphone, or have trouble remembering a time when Wi-Fi wasn’t everywhere, but many of today’s most relied-upon technologies would not have been possible—or even dreamed of—if it weren’t for the game-changing inventions that came before them. And while it’s easy to take many of the marvels of design and engineering we interact with on a daily basis for granted—think toilets, seat belts, and suspension bridges—it’s just as easy to overlook how a handful of more surprising inventions, like the Super Soaker or the pizza saver, have affected the world around us. From blood banks to barcodes and beyond, here are the stories behind 20 inventions that changed the world.

1. Suspension Bridges

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Suspension bridges are nothing new; there’s one in China that until recently used bamboo that’s at least 1000 years old, and may be over 2000. But the modern suspension bridges that came along in the 1800s were something else altogether: They were cheaper to build, easier to repair, and provided plenty of leeway in case of flooding. Eventually, the bridges allowed for passage over far larger bodies of water and could withstand violent storms and the ever-increasing weight of foot and vehicle traffic in cities (not to mention drastically cutting down travel times). In the middle of the 19th century, engineer John A. Roebling saw that the Allegheny Portage Railroad was using breakable hemp ropes, leading him to create a way to spin and manufacture wire rope, a technology Roebling would soon put toward suspension bridges. Eventually, the wire could be spun and anchored on site, which helped speed up the construction process.

Roebling’s innovations led to his designs for the Niagara River Gorge Bridge, the Sixth Street Bridge in Pittsburgh, and the famed Brooklyn Bridge in the second half of the 19th century. Though the Brooklyn Bridge was John Roebling’s basic design, his son, Washington, took over the project as chief engineer following his father’s death in 1869. Then, after Washington became mostly confined to his home following a battle with decompression sickness (or “the bends”), his wife, Emily, took on many of his responsibilities. During a time when women were kept far away from STEM fields, Emily learned about cable construction, stress analysis, and other principles of suspension bridge engineering, and was a key figure in the completion of the project.

Today, suspension bridges are located in all corners of the globe, allowing people to safely and easily travel across great chasms and bodies of water. And these bridges are no longer suspended only over simple rivers—Japan’s Akashi Kaikyo Bridge stretches 12,828 feet across the Akashi Strait and features a main span that is 6527 feet long.

2. Toilets

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Dry and flush toilets have been around for thousands of years, and while many of us take these pieces of porcelain hardware for granted these days, there’s no doubt that life would look much different—and much worse—without them. “Toilets are the key to a thriving, healthy society,” Kimberly Worsham, sanitation expert and founder of FLUSH (Facilitated Learning for Universal Sanitation and Hygiene), tells Mental Floss. Having a designated place to do your business cuts back on outbreaks of infectious diseases like cholera and typhoid—both rampant in urban areas before flush toilets (and indoor plumbing and sewers) were widely used. And in the case of dry toilets, the waste deposited there can be processed for agricultural use.

Typically, people date the modern flush toilet to John Harington, godson to Queen Elizabeth I, but there were flush toilets well before he got involved (one in Knossos, which dates back to the 16th century BCE, was even connected to a sewer). “Flush toilets like his had been available to Western Europe during the Roman Empire, but after Rome fell, Europe essentially resorted to sh***ing outside again,” Worsham says. “All of those systems fell into disrepair.” (Other areas of the world, like East Asia and areas of the Middle East, still used toilets even as Western Europe went backward.)

The options available at the time Harington was innovating were chamber pots, garderobes—which Worsham describes as “dreadful closets with holes in the ground”—or going to the bathroom outside. Harington wanted to bring the toilet back in and make going to the bathroom a more comfortable experience, but his invention left a lot to be desired: Instead of connecting to a sewer, it had a pipe that went straight down into a lower chamber that would eventually need to be emptied by some unlucky person. Even worse, its design meant that the toxic, flammable gases released when urine and poop decompose could come wafting back up, creating potentially deadly situations. It didn’t catch on; Harington built just a handful of models.

Then, in 1775, a Scottish watchmaker named Alexander Cumming developed the S-trap, a piece of plumbing that attaches to the back of the toilet. “This was revolutionary because it used water in the trap to keep the toxic gasses from getting back into the home and the poo and pee from easily sliding back into the toilet,” Worsham says. “Once Cumming patented his design, we had something like a flush toilet renaissance.” Tinkering with toilets commenced in earnest, with people like Thomas Crapper (who, according to Worsham, “created a killer marketing campaign for toilets”) getting involved. Once materials to make toilets became cheaper, they became more common, and the world got much safer. “We saw mortality rates decline,” Worsham says. “It also made our living spaces far less sh***y—literally.” Bodily waste deposited into flush toilets went into sewers or septic tanks, which meant it wasn’t on the street or in drinking water.

That said, there’s still a long way to go to make sure everyone has access to a toilet: According to Worsham, “1 in 4 people in the world lack access to basic toilets, and 1 in 2 lacks access to safely managed toilets—toilets where the waste is never put back into the environment untreated.” Without toilets, people are sicker and miss both work and school more often, which can lead to poverty traps and inequality. Thankfully, toilet tinkering hasn’t stopped: “There have been some really great projects by social enterprises and non-governmental organizations in different parts of the world working to build newer, better, more environmentally-friendly toilets,” Worsham says. “There’s also been some really neat innovation in integrating fecal waste from the toilets with organic waste—a.k.a. food scraps—and treating them to create great agricultural products like fertilizer and animal feed. We’re thinking circular economies here, and it’s exciting.”

3. The Walkman

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Though many of today’s kids didn’t know what a Walkman was until they saw Chris Pratt’s Peter Quill flaunt one in 2014’s Guardians of the Galaxy, they pay unofficial homage to the device every time they play a song on their smartphone. Transistor radios had been around since the 1950s, but it was Sony co-founder Masaru Ibuka who really revolutionized the idea of playing whatever you want wherever you are (provided that you had the cassette tape on hand). For Ibuka, he really wanted something he could use to listen to music on flights. The Sony Walkman debuted in Japan in 1979 (and the U.S. in 1980) and quickly became the It Girl of the ’80s. The Walkman itself was compact, lightweight, and portable, and so were its headphones. As new devices debuted over the years—from Sony’s Discman to Apple’s iPod to smartphones and the Bluetooth headphones of today—the focus on those qualities never wavered.

4. The Pill

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By the end of the 19th century, bicycles were offering women a relatively cheap, easy form of independence. Their movements, and the clothing they wore, became less restricted. Decades later, a new item would hit the market and further revolutionize women’s rights: the Pill.

Hormonal birth control pills (often shortened to just the Pill) weren’t the first oral contraceptive; people had long relied on various concoctions, such as drinking mercury or toxic pennyroyal. By the early 20th century, a push for better contraceptives was rising in the U.S.—Margaret Sanger opened America’s first birth control clinic in 1916, for example, though it was raided and shut down. Work on a contraceptive pill didn’t begin until the 1950s. A biologist named Gregory Goodwin Pincus and a gynecologist named John Rock, with encouragement and funding from Sanger and wealthy philanthropist Katharine McCormick, teamed up to develop a “magic pill” that could prevent pregnancy. “I would argue that effective contraception was probably in the whole of the 20th century the most important change for women,” Linda Gordon, author of Woman's Body, Woman's Right: A Social History of Birth Control in America, told Allure.

When the Pill first hit the market in 1957, it was only approved to help regulate menstruation [PDF]; even after the FDA approved the Pill for contraceptive use in 1960, it still wasn’t readily available. In some U.S. states, it remained illegal for unmarried women to purchase the pill until 1972. Oral contraceptives have evolved since their original debut; today, there are many brands on the market, and people can now choose from a variety of monophasic, biphasic, and triphasic options, which provide varying amounts of estrogen and progestin.

The creation of the Pill did more than give women control over their sexual health and fertility—it allowed them to choose to marry later, seek additional education, and advance in their careers. As Vanessa Grigoriadis wrote in New York magazine, “These days, women’s twenties are as free and fabulous as they can be, a time of boundless freedom and experimentation, of easily trying on and discarding identities, careers, partners. The Pill, which is the most popular form of contraception in the U.S., is still the symbol of that freedom.”

5. Super Soaker

For decades, squirt guns were flimsy pieces of plastic that could barely muster enough power to water a houseplant. Then the first Super Soaker—then called the Power Drencher—hit the market in 1990, bringing along with it a Schwarzenegger-esque machismo and a sophisticated air-pressure system that promised to drench unsuspecting targets from far further than previous water guns. The allure of wreaking havoc at family get-togethers and school functions was apparently too much for kids to pass up, and more than 2 million guns flew off the shelves in its debut year. Al Davis, the former executive vice president of Larami, wrote in his book Super Soaker that “The deliveries would come into the stores, and the clerks wouldn’t even have time to put them on the shelves. They’d just take them out of the boxes and sell them to the kids waiting in line for them.”

In its first 25 years on the market, more than 175 different variations of the high-powered water gun were released, racking up over $1 billion in sales in the process. Hasbro bought Larami and the Super Soaker brand in 1995, and to this day, the company continues to release bigger models that promise to unleash more water-fueled mayhem every summer.

When the Strong National Museum of Play inducted the Super Soaker into its National Toy Hall of Fame in 2015, former Curator Patricia Hogan noted, “[The] Super Soaker had a big impact on neighborhood play. The small squirt guns of the past had required close-in work to engage the opposition. The long, drenching reach of Johnson’s invention requires a quick retreat from a soggy assault or a good chase, meaning that kids with Super Soakers do some serious sprinting. Calculating the distance to target and the physics of velocity and arc requires kids to use their brains. Contemplating strategies and tactics and puzzling out plans forces kids to analyze the best approaches to triumphal ends. And if kids get soaked in the process? It’s all good clean fun.”

None of this would have been possible if not for the outside-the-box thinking of former NASA engineer Lonnie Johnson. He got the idea for the Super Soaker while testing a new type of heat pump he had created that used water as a coolant in the early 1980s. While the heat pump worked fine, he also realized it was pretty fun to shoot concentrated streams of water from the pump across his bathroom.

“I was having trouble getting people to understand the hard science inventions I had like a heat pump or the digital measuring instrument,” Johnson told Forbes. “I thought the toy was something anyone could look at and appreciate.”

Though Johnson holds over 100 patents and worked on NASA’s Galileo mission to Jupiter, his reinvention of the water gun, from 29-cent novelty to summer staple, is something that generations of kids—and some unwitting bystanders—will never forget.

6. The Blood Bank

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Less than a century ago, patients requiring a blood transfusion were in a race against time. There was no organized network for people to donate blood, and because blood was difficult to preserve, there was no way to store it for future use. Patients had to find their own blood donors before it was too late.

In 1937, after devising a technique for preserving blood for up to 10 days, physician Bernard Fantus set up the nation’s first “blood bank” at Chicago’s Cook County Hospital. People could make “deposits” of their own blood for their own use or to be given to others with matching blood types.

At about the same time, surgeon Charles R. Drew figured out a method for separating plasma from whole blood, and found that if whole blood wasn’t necessary, blood transfusions could be successfully performed with plasma alone. Plasma could be dried for long-term storage in blood banks. As World War II decimated Europe, Drew and the American Red Cross launched a groundbreaking program to collect donated plasma in the U.S. and ship it to Britain, essentially creating a national system for blood donation. During the war, he collaborated with the Red Cross to set up “bloodmobiles”—mobile blood donation centers that made sustaining blood banks more practical. Today, about 13.6 million units of whole blood and red blood cells are collected in the U.S. each year, saving countless lives.

7. Space Telescopes

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When Lyman Spitzer proposed the invention of a space telescope in the 1940s, humans could look at our universe only through land-based instruments. Earth’s atmosphere acted like a veil between the land-based telescopes and space, blurring images and hindering detection of far-off celestial phenomena. Spitzer’s research paved the way for the Hubble Space Telescope, the first space-based major optical telescope, launched in 1990 and named for the American astronomer Edwin P. Hubble.

Over its three decades in orbit, Hubble has determined the age of the universe (13.8 billion years), accurately measured the distance to a neighboring galaxy, and spotted numerous moons and exoplanets, in addition to revealing the beauty of the universe through stunning photographs. “The Hubble space telescope has brought about a visual revolution, more significant than any recent work of art in transforming the way we see ourselves and the cosmos,” art critic Jonathan Jones wrote in The Guardian. This year, NASA is scheduled to launch the James Webb Space Telescope, the largest and most technologically advanced space telescope ever built, to unravel more secrets of space.

8. The Pizza Box and Pizza Table

Glane23, Wikimedia Commons (pizza saver) // CC by 3.0; Vasko (pizza and box), Julia Lemda (background) // iStock via Getty Images Plus

The pizza industry has undergone numerous innovations in recent decades, but one element that has remained largely the same is the box your pie comes in. Domino's Pizza founder Tom Monaghan changed the game in the early 1960s when he worked with Triad Containers in Detroit to develop the modern pizza box. Prior to this, pizzas were delivered in bags or paperboard bakery boxes. These containers were flimsy and often crumpled under the intense heat of the pie before they reached their destinations. Domino’s corrugated cardboard containers were much more durable. They withstood grease and kept pizzas warm while releasing steam through strategically placed openings. Most importantly, the sturdy boxes were stackable, opening the door to mass deliveries.

But there was one area where the simple design fell short: The top of the box sometimes collapsed and stuck to the top of the pizza. The answer to this issue was the pizza saver, which Carmela Vitale patented in 1985. Shaped like a miniature patio table, the plastic device keeps the box lid separate from the pizza, thus keeping the cheese and toppings intact throughout the delivery journey. Vitale was a city council member—not a pizza salesperson—but she had eaten enough delivery pizza to notice a problem and come up with an ingenious solution.

9. X-Rays

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One fall evening in 1895, Wilhelm Röntgen, a German physics professor, was experimenting with the conduction of electricity through low-pressure gases when he accidentally discovered a mysterious ray capable of making a chemical-coated screen fluoresce a few yards away. He went on to put objects between the tube and the screen to see the shadows they produced—and when he tried it with a hunk of lead, he saw shadows of not just the lead but the bones in his hand. Further experimentation showed that the screen could be replaced by a photographic plate—and the X-ray was born.

Röntgen named it X-strahlenstrahlen being German for “beam” or “ray,” and X being used in mathematics to indicate an unknown quantity [PDF]. Röntgen's discovery revolutionized the way doctors detect disease and injury, from breast cancer to broken bones. Today, X-rays are also used to find cracks in everything from aircraft wings to nuclear reactors—helping make the modern world quite a bit safer. “Thanks to [Röntgen's] invisible light,” radiologist Richard Gunderman wrote in The Conversation, “we now operate with a much deeper understanding of the universe we inhabit, the molecules and cells of which we are composed[,] and the diseases that threaten our lives.”

10. Wildlife Cams

The first “wildlife cams” were invented by Pennsylvania Congressman and photography enthusiast George Shiras around the end of the 19th century. He got the idea from a hunting technique used by the Ojibwa tribe called jacklighting, in which a fire is built in a pan and placed in the front part of a canoe while the hunter sits in the bow. “The glow makes it possible to distinguish the animal, whose attention is caught by the flames, causing it to stand still with an expectant air,” Sonia Voss, who curated an exhibition of Shiras’s photographs, told National Geographic. “At the rear of the canoe, the hunter, cast into the shadows, only needs to aim between the animal’s eyes, which reflect the flames and stand out like two bright beacons in the night. In the photographic version, the fire is replaced by a kerosene lamp and the trigger of the rifle by the shutter release of the camera.” Later, Shiras graduated to cameras equipped with flash and tripped by a string.

Today, critter cameras have evolved to be so light that they can be strapped to marine life, are battery powered so they can be left in nature for months at a time, and have been attached to robots to get closer to dangerous creatures than ever before, giving us an unprecedented look into the lives of the animals we share the planet with, and the world they inhabit—and helping us make plenty of scientific discoveries along the way. Thanks to wildlife cameras, we know that fishers are breeding in Washington state for the first time in decades; the hairy-nosed otter—the world’s most endangered otter species—is once again lurking within Malaysia; and the rare Siamese crocodile is still slyly slipping around the waters of Thailand. Cameras have also snapped footage of previously unknown species, such as Tanzania’s grey-faced sengi (a species of elephant shrew). In 2020, trail cameras were essential in allowing scientists to continue their field research and gather data remotely during long stretches of COVID-19 lockdowns and travel restrictions.

11. Duct Tape

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Duct tape was the brainchild of Vesta Stoudt, an Illinois mom whose two sons were in the Navy. Stoudt worked at Green River Ordnance Plant packing and inspecting boxes of ammunition. The boxes were sealed with paper tape, dipped in wax, and had a tab to open them. Stoudt noticed that the boxes had a flaw: The tape was flimsy and tabs often tore off, which meant that soldiers couldn’t quickly open the boxes when they were under fire. Why not create a cloth-based waterproof tape to seal the boxes? She asked her supervisors, but they weren’t supportive, so she escalated the matter … straight to President Franklin Delano Roosevelt. “I suggested we use a strong cloth tape to close seams, and make tab of same,” she wrote. “It worked fine, I showed it to different government inspectors they said it was all right, but I could never get them to change tape.”

The president sent her letter to the War Production Board, her idea was approved, and the rest is history. Duct tape has been a quick fix for everyone from your average joe to physicists (who use it on their particle accelerators) to astronauts (duct tape helped them make repairs on the moon). When the three crewmembers of Apollo 13 were forced to transfer to the lunar module, duct tape helped them survive—according to Northrop Grumman, the vessel was designed to hold two people for 36 hours, but after the accident, had to hold three for over 86 hours. They used the adhesive (along with cardboard, plastic bags, and space suit components) to adapt their square carbon dioxide filters to the module's round holes. Jerry Woodfill, a NASA engineer who assisted the team from the ground, later told Universe Today, “Of course … the solution to every conceivable knotty problem has got to be duct tape! And so it was.”

12. Barcodes

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On June 26, 1974, a grocery store cashier at Marsh Supermarket in Troy, Ohio, passed a pack of Wrigley’s Juicy Fruit chewing gum over a scanner—and the item and price were automatically registered. It was the first time an item with a barcode had ever been purchased.

The inventors behind this marvel of commerce were N. Joseph Woodland and Bernard Silver, who envisioned a system of lines that could identify consumer products by using encoded information read by an optical scanner. It all started when Silver, a grad student at Drexel, overheard the president of a local food chain talking to the dean about the need to automatically obtain product information. The dean wasn't interested in pursuing the idea, but Silver mentioned it to his colleague Woodland, who thought the idea had so much promise that he quit his job and moved to Florida to pursue it. Ultimately, Woodland devised a system inspired by Morse code (which he had used as a Boy Scout) as well as the movie sound systems of the 1920s. It was later refined with help from IBM employee George Laurer, and became the basis for getting through checkout lines faster.

Today’s standard barcodes are known as universal product codes, or UPC-A, and are comprised of 12 digits. The first is a product category—3 denotes a health-related item, for example, while the rest point to the manufacturer and specific product. The more recent QR barcodes commonly recognized by smartphones can deliver information in an instant. Barcodes are used across a variety of industries and can boost productivity eight to 10 times compared to manual data entry. It all makes for a much speedier transaction, but not always: Aldi grocery employees sometimes memorize popular product barcodes so heavy items can remain in the cart.

13. Seat Belts

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The idea of a seat belt for transportation safety doesn't begin with Nils Bohlin, the Swedish engineer who conceived of a three-point shoulder and lap belt for automobiles in 1958. Other innovators, like 19th century aviator George Cayley, recognized a need to keep humans from being ejected out of planes and other moving vehicles. But it was Bohlin, a Volvo engineer, who sought to improve upon the two-point lap belts, which could sometimes do more harm than good in the event of an accident. (At high speeds, the belts were capable of causing internal injuries.) By stabilizing the torso with a shoulder strap, drivers and passengers were kept in place without resorting to the more burdensome four-point belts worn by pilots or an earlier Y-shaped belt placed over the stomach. In what could only be described as an act of corporate selflessness, Volvo allowed any car manufacturer to duplicate the belt. At the time of Bohlin’s death in 2002, it was estimated his invention had saved well over a million lives.

14. The Microwave

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During World War II, engineer Percy Spencer aided the U.S. war effort through his work on magnetrons—tubes that generate electromagnetic waves for radar—while working for tech company Raytheon. His work didn’t end with the war. In 1945, Spencer was tinkering with magnetrons when he noticed the peanut cluster candy bar in his pocket had suddenly transformed into a “gooey, sticky mess.” It didn’t take long for him to realize the magnetron’s microwaves were responsible, prompting him to develop a microwave oven that people could use to heat food more deliberately. The refrigerator-sized “Radarange” debuted in the mid-1940s and was originally meant for restaurants and airplanes rather than regular homes. (Its $1250 price tag—nearly $17,000 today—would have made widespread success in that realm unlikely anyway.)

Designs improved and costs decreased over time, and the 1967 edition of the Radarange was a hit among homemakers. By the mid-1970s, the microwave oven—eventually just “the microwave”—was becoming a mainstay in U.S. kitchens, and not just for leftovers. Manufacturers marketed the appliance as a faster, easier, (literally) cooler alternative to conventional ovens. “Make the greatest cooking discovery since fire,” actress Barbara Hale said in a 1972 Radarange ad that Mad Men’s Don Draper surely would have wished he’d come up with himself. A 1971 ad for General Electric’s Just-A-Minute oven emphasized that “with the special timer, control settings, and recipe booklet that come with the oven, practically all the guesswork is taken out of cooking,” a boon to unconfident cooks everywhere. Full-fledged cookbooks cropped up, too—Madame Benoit’s Microwave Cook Book, Barbara Kafka’s The Microwave Gourmet, and so on—featuring everything from duck à l’orange to “Elegant Beef Dinner.” One 1978 cookbook even recommended making pie in the microwave (to get around the lack of browning, it was advised, just throw some yellow food coloring in there). And when Swanson debuted its plastic, microwave-safe trays in 1986, the microwave and the TV dinner entered into a marriage of convenience that worn-out adults would rely on for decades to come.

15. The Can Opener

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Decades after people started storing food in tin cans, someone finally came up with a way to crack them open that didn’t involve a chisel and a hammer (or some other dangerous tool). In the mid-19th century, a series of inventors built what were known as lever knives—not too dissimilar to the can opener on a modern Swiss Army Knife, and by 1870, William Lyman innovated a design that included a rotary cutte. But it wasn’t until the 1920s that Charles Arthur Bunker arrived on the scene with a patent that featured handles you squeeze together to safely puncture the lid and a handle you twist to propel a sharp little wheel along the rim. If that sounds familiar, it’s probably because today’s manual can openers are pretty much the same.

16. Velcro

Like the button (which dates back thousands of years, though the buttonhole is a more recent innovation) and the zipper (invented in the 19th century) that came before it, Velcro revolutionized clothing—and we have old-fashioned curiosity to thank for its invention. In the 1940s, George de Mestral and his dog returned from a hunting trip covered in burdock burrs. Intrigued, de Mestral whipped out his microscope to find out what, exactly, made the burrs stick. He discovered that the burrs were covered in little hooks, and that provided de Mestral, a serial inventor, with a burst of inspiration: If he could create a fabric that mimicked the burrs’ hooks, and combine it with fabric loops those hooks could latch into, he’d have a middle ground between fasteners like buttons and zippers.

It took him some time to find a manufacturer to create his fabric; many didn’t think it could be done. But de Mestral persevered and continued to innovate on his idea until he had a product that worked, and Velcro—a trademarked combination of the French words velours and croche, meaning “velvet” and “hook,” respectively—debuted in the early ‘60s. Since then, it has proved as useful as de Mestral thought it would: NASA has used it to anchor equipment in space missions and during walks on the moon; Mead made use of the material as fasteners on its iconic Trapper Keepers; and, of course, it’s used in shoes and clothing, where it’s particularly helpful to people who have difficulty with zippers and buttons (or their caretakers).

17. Air Conditioning

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Since its introduction at the turn of the 20th century, the air conditioner has transformed the quality of life in regions with warm climates—but the first modern air-conditioning unit wasn’t invented for people at all. It was created for a printing press.

In 1902, a 25-year-old engineer named Willis Carrier was asked to come up with a way to control the humidity at the Sackett & Wilhelms printing plant in Brooklyn, where the sweltering summer days frequently messed with the color register. After early tests with rollers, burlap, and calcium chloride brine, Carrier hit on a device that sent chilled water through heating coils. The system was installed later that same summer at the printing plant alongside fans, perforated steam pipes, and other accouterments. It was a huge success, and reportedly had the same cooling effect as 108,000 pounds of ice per day.

Carrier's invention was sold everywhere from flour mills to razor factories, and air-conditioning went on to reshape both architecture (by allowing for skyscrapers where people didn't broil on top floors) and nations, making the development of modern metropolises in sun-scorched places like Singapore, Shanghai, the Sun Belt, and Dubai possible. It also, of course, made everyday life more pleasant (and productive) for millions, if not billions. Ironically, the large amount of energy air conditioners consume has contributed to climate change, making the need for artificial cool air more vital than ever. “It’s not a matter of going back to the past. But before, people knew how to work with the climate,” Malaysian architect Ken Yeang told The Guardian. “Air conditioning became a way to control it, and it was no longer a concern. No one saw the consequences. People see them now.”

18. Radio

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The story of the invention of the radio is about a race against time between two scientists—and the power of patents.

Guglielmo Marconi, an Italian inventor, sent and received his first radio signals in 1894, and patented his invention in 1896 in England. Three years later, Marconi sent wireless signals across the English Channel, and two years after that, he claimed that he received a message sent from across the Atlantic (that claim, however, is controversial).

At roughly the same time Marconi was at work in Europe, inventor Nikola Tesla was working on a similar invention in America. Tesla invented the Tesla coil—which sent and received radio waves—in the 1890s. He was all set up for a long-distance experiment in 1895, but a fire broke out in his lab, interrupting the experiment. Two years later, Tesla applied for his patent in the United States.

Marconi and Tesla’s paths converged in 1900, when Marconi applied for a patent in the U.S.—which was denied because Tesla’s had been approved earlier that year.

Undaunted, Marconi continued to apply, and in 1904, the U.S. declared him to be the creator of the radio. This, along with the fact that Marconi had won a Nobel Prize for the technology, enraged Tesla. In 1915, he sued Marconi for patent infringement, but lacked the financial resources to pursue the case.

But beyond the courtroom drama, radio was already at work transforming the world. In 1910, it helped catch Dr. Hawley Harvey Crippen, a man who was accused of killing his wife and escaping to Canada on a ship with his lover; he was caught thanks to Marconi’s wireless telegraph, which sent radio waves, and a very clever ship captain. On August 31, 1920, the first radio news program was broadcast by a station in Detroit, and the first ad played on the radio in 1922, changing the world of advertising. Radio was also used during both World Wars.

From protests, music, famous speeches, and political unrest, the radio has broadcast many iconic moments and connected the world in a way Marconi and Tesla probably never imagined. Some have gone so far as to say that radio changed everything; as Jack Lule wrote in his book, Understanding Media and Culture, the radio became “an instrument of social cohesion as it brought together members of different classes and backgrounds to experience the world as a nation.”

As for who came out on top in the radio patent war? Tesla finally got his victory in 1943, when the Supreme Court upheld that his patent had priority. But it was a win the inventor never got to celebrate: He had passed away earlier that year.

19. Aquariums

While keeping fish as pets may have begun with the Romans, the first glass aquarium wasn’t created until 1832, when seamstress-turned-scientist Jeanne Villepreux-Power got tired of studying dead specimens in her lab. Observing marine life wasn’t as easy as observing animals on land, and she wanted to come up with a way to keep cephalopods—especially the paper nautilus—alive outside of the ocean.

To further her research, Villepreux-Power created three different types of aquariums: one for indoor study, one for shallow water, and one to be anchored to the ocean floor. The indoor glass aquarium allowed her to discover that the Argonauta Argo produced its own shell at the larva stage, as well as the fact that the animals can repair their shells within a few hours. She also came up with the idea of repopulating rivers using fish raised in aquariums. (Unfortunately, most of Villepreux-Power’s research was lost in a shipwreck, and she never rewrote her findings.)

Many would improve on her work, from Nathaniel Bagshaw Ward (who turned a terrarium upside down) to Anna Thynne (who created the first marine aquarium filled with coral and seaweed) to Robert Warington [PDF] (who published his findings after managing to keep the environment in a 12-gallon tank stable). Two decades after Villepreux-Power’s invention, the first public aquarium opened in London in 1853; a few years after that, P.T. Barnum built an aquarium inside his Barnum’s American Museum in New York, which visitors enjoyed for until the museum burned down in 1865.

Since then, aquariums have become a favorite pastime for people around the world: According to American Humane, 700 million people around the world visit zoos and aquariums annually. Like zoos, aquariums can help with conservation efforts and protect endangered species—and like zoos, they can be controversial, as we debate how humane it is to keep large marine mammals like dolphins, orcas, and beluga whales in tanks much smaller than their natural environments. Still, many aquariums aren’t just for entertainment, but are also focused on exactly what Villepreux-Power was when created an aquarium in the first place: studying and learning.

20. The Lightbulb

The Print Collector/Print Collector/Getty Images (lightbulb); Julia Lemba (background) // iStock via Getty Images Plus

Lighting a home used to be a hazardous experience: Open flames on candles and in fireplaces could set things ablaze. The gas lamp, invented near the end of the 18th century, was a definite upgrade, but it had its own set of issues, from fumes to being hard to maintain to the potential for explosions.

Enter: the lightbulb.

While Thomas Edison is often credited with inventing the lightbulb, there were many scientists and researchers who worked on a version of the device before Edison. Inventors like Humphry Davy (creator of the arc lamp) demonstrated how electricity could be used to create light. In the first half of the 19th century, a series of improvements were made—so much so that in the 1840s later-Sir William Grove was able to give a lecture fully illuminated by electric light. But the light was exceedingly expensive, up to 4 shillings an hour (16 pounds or $22 in today’s money) and early lightbulbs themselves were both expensive to make and unreliable.

There wasn’t a breakthrough until 1878, when chemist Joseph Swan replaced the expensive platinum filament with a cheaper carbonized paper one that also had longevity. Edison demonstrated his lightbulb in 1879, one year after Swan. After a long patent infringement lawsuit, the two decided to combine forces and formed the company Edison-Swan United. Later in life, Edison would choose his lighting system as his greatest invention.

Even Edison and Swan’s bulb wasn’t perfect, however, and many scientists continued to improve on its design—including patent expert Lewis Latimer, who streamlined and improved the carbon filament by encasing it in cardboard instead of bamboo, an innovation that allowed for longer-lasting bulbs.

It’s not hyperbole to say that the modern lightbulb changed how society functioned. Beyond making the home safer, it helped cut back on health problems created by things like gas fumes and smoke inhalation, paved the way for longer working hours, impacted building design, and kicked off the creation of massive infrastructure like the electric grid. Lightbulbs went into everything from cars to airplanes to trains, increasing the rate of travel—and making it much safer. And the lightbulb has left its mark symbolically, too. “Even though this invention, Edison’s bulb, is 135 years old at this point,” Ernest Freeberg, author of The Age of Edison: Electric Light and the Invention of Modern America, said in 2015, “we still use [it] as the universal symbol for a great idea, for a stroke of inventive genius, for this Eureka moment.” Today, scientists work on improving the lightbulb every year, leading to more energy-efficient bulbs—and joining the long line of scientists and engineers whose bright ideas have changed history.

A version of this story ran in 2020; it has been updated for 2023.