A common technology used to generate power, usually via Plasma.
Nuclear Fusion generally involves super heating fuel to several times the temperature of the sun to create plasma, generating a cycle of fission and fusion within the fuel's molecules.
In most cases, this involves generating Plasma. Fuel is usually spun around and held under pressure by electromagnetic forces forcing the change into high pressure, high temperature Plasma, often many times the surface of the sun.
The most common fuels used are Deuterium/Heavy Water, while more efficient/potent and more sought after fuels include Nadriah, Spacium and Engen. They are sought after because they easily turn into plasma and are thus easier to control and produce less stress on the system. Engen in particular is a secret sought by many races, companies and civilizations in the Scorpio Galaxy. This because, as a stable form of plasma it would make Nuclear Fusion very cheap in and much safer.
Ethium is also usable, but it is not widely sough after.
Fusion devices are also used to contain some forms of Hyper-Matter such as Subspace Matter. Due to the intense internal heat, Fusion devices require materials that can withstand absurd temperatures for long periods of time.