Plasma is often referred to as the fourth state of matter, in addition to the conventional solid, liquid, and gas states). Plasma is an ionized gas consisting of approximately equal numbers of positively and negatively charged particles. There are two general forms of plasma: high-temperature plasmas that are found in stars and in fusion reactors, and low-temperature versions (ranging from 100 to 1,000 degrees Fahrenheit) used in fluorescent lighting, electrical propulsion, and semiconductor manufacturing. Plasma is the most abundant phase of matter in the universe, and all stars are huge balls of plasma. Plasma is created by zapping electrons away from their atoms, which requires the input of energy.