Microwave ovens save time spent in cooking food. A microwave is a wave that is very short, but has a high intensity. A microwave oven uses these special microwaves to cook food in about one-tenth of the time it normally takes. You can have a frozen pizza ready to eat in 3 minutes instead of 30, and a roast that would ordinarily take 3 hours to cook is ready to eat in 20 minutes More and more people are using microwave ovens in their homes.