In 1945, engineer Percy Spencer was working on radar technology when he noticed a candy bar had melted in his pocket. Intrigued, he tested popcorn and an egg—one popped, the other exploded. The cause? Microwaves from the magnetron heating food from the inside out.

Spencer and Raytheon quickly developed the first microwave oven. The 1947 “Radarange” was massive, expensive, and mostly used in restaurants. But by the 1970s, compact microwaves had found their way into homes, changing kitchens forever.