Fusion energy is the energy generated by nuclear fusion processes. Fusion is the process which powers the sun and the stars. It is energy that makes all life on earth possible. It is called 'fusion' because the energy is produced by fusing together light atoms, such as hydrogen, at the extremely high pressures and temperatures which exist at the centre of the sun. The aim of fusion research and development is to create conditions on earth which are sufficient to generate many fusion reactions which may be harnessed to produce large amounts of thermal and/or electrical power.