Fusion is the process that heats the Sun and all other stars, where atomic nuclei collide together and release energy (in the form of neutrons). To get energy from fusion, gas from a combination of types of hydrogen – deuterium and tritium – is heated to very high temperatures (100 million degrees Celsius). One way to achieve these conditions is a method called ‘magnetic confinement' – controlling the hot gas (known as a plasma) with strong magnets. The most recognised device for this is the ‘tokamak', a Russian word for a ring-shaped magnetic chamber.