What was the first food cooked in microwave?

The first food intentionally cooked in a microwave oven was popcorn. Percy Spencer, an American self-taught engineer and inventor, discovered the microwave heating effect in 1945 while working on radar technology for the Raytheon Corporation. During an experiment, he noticed that a candy bar in his pocket had melted due to the microwave radiation emitted by the magnetron, a vacuum tube used to generate microwaves.