The microwave oven was invented by mistake when an engineer, by the name of Percy LeBaron Spencer, noticed that the radiation from a magnetron tube he is testing melted the chocolate bar he had in his pocket.

During World War II, Spencer was one of the leading experts in radar tube design working for Raytheon, a weapons and military electronics contractor associated with the American Department of Defense. He headed the division tasked to develop and produce combat radar equipment for M.I.T.’s Radiation Laboratory.

While building magnetrons one day, Spencer noticed the candy bar he had in his pocket had melted while he was standing in front of an active radar set. Intrigued, he investigated on what caused the candy bar to melt. He experimented with food, including popcorn kernels, which became the world’s first microwaved popcorn.

Spencer then took a kettle and cut a hole on its side. He placed a whole egg in the kettle and positioned the magnetron to direct the microwaves into the hole. The result was the egg exploding in the face of one of his co-workers, who were looking in the kettle to observe.

Spencer created the first true microwave oven by attaching a high density electromagnetic field generator to an enclosed metal box. The magnetron emitted microwaves into the metal box blocking any escape, allowing for controlled and safe experimentation. He then placed various food items in the box, while observing effects and monitoring temperatures. His work progressed well, so Raytheon filed a patent on October 8, 1945 for a microwave cooking oven, eventually named the Radarange.

The first commercially produced microwave oven was about 6 feet tall, weighed about 750lbs, and cost about $5000. In 1967 the first relatively affordable ($495) and reasonably sized (counter-top) microwave oven was released for sale. Today, no kitchen is complete without a microwave oven.

Spencer became Senior Vice President, and a Senior Member of the Board of Directors at Raytheon. He received 300 patents during his career there. He received no royalties for his invention, but he was paid a one-time, two-dollar gratuity from Raytheon - the same token payment the company made to all inventors on its payroll at that time, for company patents.

Had Spencer owned the patent for his invention, he would have been one of the richest men in history.