In 1945, Percy Spencer, a self-taught engineer from Howland, Maine was working on an active radar set when he noticed something strange. A chocolate bar in his pocket had started to melt.

The idea for dielectric cooking with a shortwave transmitter had already been demonstrated by Westinghouse at the 1933 Chicago Worlds Fair. Spencer picked a winner, however, when he tried his hand at cooking something irresistible with this method, popcorn. Raytheon filed a United States patent for Spencer’s microwave cooking process and by 1947 the first commercially available microwave oven was built.

On National Microwave Oven Day, we still love celebrating with something delicious like popcorn.

Today we also celebrate: World Trick Shot Day, Saint Nicholas Day, National Pawnbrokers Day, National Miner’s Day, and National Gazpacho Day.