In order for a fusion reactor to function well, one of the important conditions to be met is a high temperature at 108 million Kelvin. This is six times hotter than the temperature of the sun's core. At this temperature, the element hydrogen's state is a plasma, not a gas, where the atoms are stripped of electrons and thus can move freely. This is an ideal condition to enable the reactor to function where it enables the hydrogen atoms to gather enough energy for the reaction which will occur in the later stages of the process.
