Appliance that cooks food by means of high-frequency electromagnetic radiation .
A microwave oven is a relatively small, boxlike oven that raises the temperature of food by subjecting it to a high-frequency electromagnetic field . The microwaves are absorbed by water, fats, sugars, and certain other molecules, whose resulting vibrations produce heat. The heating thus occurs inside the food, without warming the surrounding air. This process greatly reduces cooking time; baking and other tasks that may require an hour or more in a conventional oven can be completed in minutes in a microwave oven.