Percy LeBaron Spencer, an engineer, was working on radar for the army. One day, he was walking past a machine when the chocolate bar in his pocket melted. He was curious, so he did a test. He put a small bowl of popcorn in front of the machine. As expected, a minute later it started popping and jumping out of the bowl. Spencer realised the microwaves from the radar were heating the food. Next, he made a metal box and sent microwaves into it through a hole. When he put some food in the box, it cooked. This was the first microwave oven invented totally by chance