In addition to having a great range of frequencies to transmit information, microwaves are used every day in kitchens around the world. Microwave ovens generate 2.4 GHz waves and scatter them throughout the oven. The microwaves excite water and fat molecules into resonance and cause them to rotate, increasing their thermal energy. Different kinds of molecules absorb the energy at different rates, so some foods are heated more than others. Microwave-safe containers are made of materials that do not absorb microwave energy and so remain cool.