That’s the story from the inventor. In 1945, Raytheon engineer Percy Spencer accidentally invented the microwave while working with radar technology. The discovery happened when a radar magnetron melted a nut cluster in Spencer's pocket. Intrigued, Spencer tested the machine's effects on food, causing an egg to explode and popcorn to pop. He then filed a patent for a “Method of treating foodstuffs”. The first microwave models were huge, weighing over 750 pounds and standing 6 feet tall.