A microwave oven (often referred to colloquially simply as a "microwave") is a kitchen appliance that heats food by dielectric heating accomplished with radiation used to heat polarized molecules in food. Microwave ovens heat foods quickly and efficiently, because excitation is fairly uniform in the outer 1 inch (25 mm) to 1.5 inches (38 mm) of a dense (high water content) food item; food is more evenly heated throughout (except in thick, dense objects) than generally occurs in other cooking techniques.^{[citation needed]}

Dr. Percy Spencer invented the first microwave oven after World War II from radar technology developed during the war. Named the 'Radarange', it was first sold in 1947. 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 countertop microwave oven was first introduced in 1967 by the Amana Corporation, which had been acquired in 1965 by Raytheon.