A microwave oven works by channelling heat energy directly the food molecules. Thus, they rely on radiation (just like the sun) to cook food. On the inside, the device has a magnetron (microwave generator) that produces radio waves when it’s turned on. As the magnetron channels the radio waves to the food, it hits the food from all sides. That’s because the turntable, on which the food sits, keeps turning. The inside of the microwave has shiny surfaces on which the microwaves bounce back and forth, penetrating the food. The food molecules vibrate quickly, thus heating up.