When did the first microwave oven appear?

The microwave ovens origin is often traced to 1945, when Raytheon engineer Percy Spencer noticed that a chocolate bar in his pocket melted while he worked near radar equipment. Realising microwaves could heat food, he and the company developed the technology into a product. The first commercial model, the Radarange, went on sale in 1947. It was enormous, stood about as tall as a person, weighed several hundred kilograms, and was far too costly for homes. Smaller, cheaper countertop models arrived in the late 1960s and made the microwave a common kitchen appliance.