Nuclei of lighter atoms such as
hydrogen collide and fuse to produce nuclei of heavier atoms such as helium and release vast amounts of energy in the process —this is the essence of fusion. Because the energy is derived from the action of nuclei, fusion is a form of nuclear energy. It may be considered the opposite of fission, also a form of nuclear energy, which is generated when nuclei of heavy atoms split into lighter ones. Fusion is the process that powers and drives the production of energy in stars, such as our Sun.
