Raytheon turned a radar magnetron into a home oven after it melted candy.

During the war Raytheon made magnetrons, the vacuum tubes that generate the microwaves used in radar. While standing by one in 1945, engineer Percy Spencer noticed the candy bar in his pocket had melted.

Rather than shrug it off, he tested kernels of corn in front of the tube and watched them pop, then put an egg in the field and watched it cook. He understood the waves had to be agitating water molecules and heating the food from the inside.

Raytheon filed a patent on October 8, 1945, and built the first oven, a six-foot, 750-pound machine with the magnetron inside, sold as the Radarange. The patent was granted on January 24, 1950.

The first Radarange cost $5,000, so homes balked. It was not until 1967 that Amana, a Raytheon subsidiary, released a $495 countertop model, and by 1975 the countertop oven had outsold gas ranges.

The radar part's microwaves cook food by agitating water

The microwave field creates friction in water, so heat comes from inside the food not a burner

A defense component that was already cheap to make supplied a household product

One observed accident became a patent and a new product category

The first machines were too big and costly, but the mechanism still won in the end

When a product you already make does something nobody planned for, the asset is sitting in front of you; a cooking oven and a radar transmitter are the same component aimed differently.

The microwave became a near-universal kitchen appliance, present today in more than 90% of American homes (per USDA per HISTORY). Radar and the oven shared one component, and Raytheon's wartime skill produced a consumer category.