These simultaneous conditions are represented by a fourth state of matter known as plasma. In a plasma, electrons are stripped from their nuclei. A plasma, therefore, consists of charged particles, ions and electrons. There are three principle mechanisms for confining these hot plasmas - magnetic, inertial and gravity.
Inertial confinement uses powerful lasers or high energy particle beams to compress the fusion fuel.
The enormous force of gravity confines the fuel in the sun and stars.