Percy reached in his pocket and retrieved a melted candy bar, and it changed the world. It may seem strange that such a seemingly-trivial event would have such profound ramifications. After all, who hasn’t had the unpleasant experience of sticking a candy bar in one’s pocket and forgetting about it, only to be rewarded with a gooey mess? When Percy pulled his melted candy out of his pocket that day in 1945, he had the foresight to realize much more was going on than simply the loss of a tasty snack.

Percy Spencer was a self-taught engineer employed by Raytheon. He was working on improving radar technology. Specifically, he was focused on magnetrons, the high-powered vacuum tubes inside radars. While watching one of the testing units, Percy felt the peanut-cluster candy bar in his pocket grow warm. When he pulled it out, he was surprised to see it reduced to a gooey mess.

Percy was surprised, and he tried to figure out what could have caused the phenomenon. He knew that the magnetron in question produced microwaves, and he wondered if there could be a connection. On a hunch, he got some popcorn kernels and placed them in the area where he had been standing. Sure enough, the kernels began to pop, as if by magic. The next day, he brought an egg and tried the same thing. While fellow engineers gave Percy amused looks, he positioned the egg near the magnetron and told them he thought he would be able to cook the egg without any apparent source of heat. While he was explaining his premise, the egg exploded.

Percy knew he had stumbled upon something remarkable. He began to focus his attention on a way to safely cook food in a fraction of the time it had taken up to that point. In October 1945, Percy and Raytheon filed a patent application for “A Method of Treating Foodstuffs.” On April 1, 1950, the U.S. Patent and Trademark Office approved Patent No. 2,495,429, and the microwave oven was born.

The first commercial microwave oven was unlike the one you probably have in your kitchen. Known as the RadaRange, it was roughly the size of a refrigerator, weighed 750 pounds, and cost $5,000 ($58,277 in 2020 dollars). Once turned on, it took 20 minutes to warm up, but once it was ready, it was ten times more powerful than its contemporary counterparts. It could, for example, cook a potato in thirty seconds. At that price and size, it was not a commercial success. It wasn’t until 1967 that a countertop version was produced and offered for $495 ($3,866 in 2020 dollars).

With smaller and more affordable models, the kitchen innovation began to catch on. By 1975, sales of the microwave oven surpassed those of gas ranges. In 1986, one-quarter of all U.S. households owned a microwave oven. By 1997, that number grew to over 90%.

Percy died in 1970, at the age of 76. He did not get to witness society’s wholehearted embracing of his invention. As for his personal benefit, he did not receive any royalties, but he was paid $2.00 (no, that’s not a typo — it really is two dollars) as a one-time gratuity from Raytheon. This was the standard compensation for any employee who invented something on company time.