A microwave oven is an electric oven that heats and cooks food by exposing it to radiation in the microwave frequency range. This induces polar molecules in the food to rotate and produce thermal energy in a process known as dielectric heating. Microwave ovens heat foods quickly and efficiently because high water content food items can warm themselves with the energy from the radio waves. 

An American engineer, Percy Spencer is generally credited with inventing the modern microwave oven after World War II from radar technology developed during the war. Named the “Radarange”, it was first sold in 1946. Raytheon later licensed its patents for a home-use microwave oven that was first introduced by Tappan in 1955, but these units were still too large and expensive for general home use. 

The first microwave oven with a turntable was introduced between 1964 and 1966. The countertop microwave oven was first introduced in 1967 by the Amana Corporation. After low-cost microwave ovens affordable for residential use appeared in the late 1970s, their use spread into commercial and residential kitchens around the world. In addition to their use in cooking food, microwave ovens are used for heating in many industrial processes. 

Microwave ovens are popular for reheating or cooking a variety of foods. They are also useful for rapid heating of otherwise slowly prepared foodstuffs, which can easily burn or turn lumpy when cooked in conventional pans, such as hot butter, fats, chocolate or porridge. Unlike conventional ovens, microwave ovens usually do not directly brown or caramelize food, since they rarely attain the needed temperatures to produce the necessary reactions. In addition, microwave ovens have limited roles in professional cooking because the boiling-range temperatures of a microwave will not produce the flavorful chemical reactions that frying, browning, or baking may.