The first microwave oven was built in 1947. Sometime around 1946, Percy Spencer, while working for Raytheon, discovered that a magnetron developed to jam radars during World War II also melted the chocolate bar in his back pocket. Corn kernels were some of the first foods Spencer tested, and when they popped, he began attempts to heat other foods using the magnetron.
The first microwave oven was impractical for home use. It was as large as a refrigerator and weighed more than 750 pounds. Amana purchased Raytheon in 1965 and produced the first countertop microwave oven, like those used in kitchens today, in 1967.