All matter is made of particles called atoms (which make up molecules). These atoms and molecules are always in motion – bumping into each other or vibrating back and forth. Heat is a form of energy that is created through the movement of atoms and molecules. The amount of movement of molecules in a substance increases as it gains heat and decreases as it loses heat. At higher temperatures, particles have more energy. Some of this energy can be transmitted to other particles that are at a lower temperature. There are many types of electromagnetic waves. From lowest energy to highest energy there are radio waves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays. They do not affect the movement of particles in substances.