Marbles aren't just for schoolchildren. Humans have likely been playing with the tiny toys for thousands of years, as indicated by ancient Egyptian artifacts and other objects studied by archaeologists. These trinkets have been crafted from materials including clay, stone, wood, glass, and metal. But in the early 1900s, Akron, Ohio–based Martin F. Christensen changed the way the playthings are made when he invented an automated machine that produced glass marbles.

Christensen's machine ultimately paved the way for the mass production of marbles. But in the video below, you can see how they're made the old-fashioned way. Produced by The Magic of Making—a series of short educational films created along with BBC—and spotted by The Kid Should See This, the clip shows glass makers in action as they use large ovens to melt granules of sand into liquid, and as they stretch, twist, and shape the molten goo into fragile (yet still playable) creations.

[h/t The Kid Should See This]