Atomic energy is a type of energy or reactor that is generated by the splitting or fusing of atoms. It is a form of energy that is released from the nucleus of an atom, either through nuclear fission or nuclear fusion. Nuclear fission is the process of splitting an atom into two or more smaller atoms, while nuclear fusion is the process of combining two or more atoms into one larger atom. ATOMIC energy has been used to generate electricity in nuclear power plants since the 1950s, and is also used in certain medical treatments and in the production of weapons.