Nuclear Energy or Nuclear Power is the use of nuclear reactors to generate heat and electricity. It includes nuclear fission (power stations), nuclear decay and nuclear fusion. The two main types of Nuclear Energy are Nuclear Fission and Nuclear Fusion, although Fission is the only commercially viable option at the moment. Nuclear Fission involves the splitting of larger atoms into small atoms called fission products, which generate heat that is turned into energy. Nuclear Fusion combines two small atoms to produce heavier atoms, which release more energy.