'Foodkeepers' microwave dish, c 1997.

Food container which can be used to freeze, cook, serve and store food, and is designed to withstand temperatures from -40 C to +160 C. Microwave ovens use short radio waves to penetrate food which is cooked by the heat produced by the agitation of water molecules within the food. This new method of cooking was introduced in the USA in the late 1940s and in Britain in 1959 and increased the speed of cooking dramatically.