The microwave oven was patented on October 8, 1945 by the company Raytheon. At the time, it was called the Radarange. It wasn't until 1967 that the microwave was more affordable and reasonably sized.
The microwave was discovered by accident by Percy Spencer. Spencer was building magnetrons for radar sets. When the radar set was active, he noticed that the candy bar in his pocket melted. Spencer was not the first to notice, but he was the first to study it. He and his colleagues began heating food with the waves. It was during this experience that they heated popcorn kernels and created the first microwave popcorn.