Ingrid Kosar was employed as a purchasing agent for a steel company in the early 1980s when inspiration struck. She’d always wanted to own her own business, but didn’t have a clue as to where to start. Then one day in 1982, she met Bill Seliskar, who owned a company that manufactured pizza boxes. He semi-jokingly lamented to her one day that what the world needed was a container that released steam but retained enough heat to keep a pizza hot. Kosar thought the idea had merit, and pursued it. She saw a sewn bag at a craft show, and decided that a similar device could be used to keep pizzas warm.

She began experimenting with different designs and materials. She baked endless pizzas for friends and families just to test her containers. Ingrid consulted with Dominos’s, who informed her that the ideal bag would keep a pizza at 140 degrees for at least 45 minutes. When she hit upon the ideal design, she contacted Seliskar, who agreed to back her financially. Kosar patented her insulated bag in 1983, and eventually sales grew to the extent that Bill Seliskar ended up working for her as a salesperson.

Kosar’s insulated bags have expanded past the pizza market. Today, her invention keeps food warm for everyone from Meals on Wheels to private caterers to the U.S. military. Her only regret, if you can call it that, is that her product is too durable. Her repeat customers take 10 to 15 years to call back, because that’s how long her bags last.