Most people know that matter comes in three phases, solid, liquid and gas, but unbeknownst to many, there is a fourth phase: Plasma. Plasma is the most energetic of the phases. It occurrs in very high temperatures, when a gas is so heated that it becomes ionized. Plasma is given off by the sun's corona. When matter becomes Plasma, it is not considered to be a phase change because it occurrs so slowly. Because it requires so much energy to become plasma, it does not occur often on the Earth, with the exception of lightning bolts and parts of flames. Most of the matter in the rest of the universe is plasma.