Microwaves were invented in 1945. The invention is credited to Percy Spencer, an American engineer working at Raytheon Laboratories. He discovered the heating effect of microwaves accidentally when a candy bar in his pocket melted while he was near an active radar set emitting microwave signals. Spencer then experimented with heating foods like popcorn and eggs using microwave energy and filed the first patent for a microwave oven in 1945. The first commercial microwaves became available in 1946 but were very large and expensive, mostly used in restaurants, canteens, and ship galleys. The first residential countertop microwave was sold in 1967.