The microwave was invented accidently in the 1940s after a researcher walked by a radar tube and a chocolate bar melted in his pocket. Percy Spencer, a self-taught engineer, was building magnetrons for radar sets with the company Raytheon. He was working on an active radar set when he noticed that a peanut chocolate bar he had in his pocket started to melt. The radar had melted his candy bar with microwaves. The first food to be deliberately cooked with Spencer's microwave was popcorn, and the second was an egg, which exploded in the face of one of the experimenters. To verify his theory, Spencer created a high density electromagnetic field by feeding microwave power into a metal box which it had no way to escape. When food was placed in the box with the microwave energy, the temperature of the food rose rapidly. __