Energy exists in various forms and can be transferred from one form to another but not created or destroyed. Work is the transfer of energy due to a force acting on an object over a distance. Kinetic energy is the energy of motion while potential energy is stored energy due to an object's position or composition. Chemical energy powers living things through photosynthesis and can be stored for later use. Nuclear energy is released through fusion in stars and fission in bombs and reactors. According to Einstein's equation, matter and energy are directly related and matter can be converted to energy.