Plasma

From HvWiki

Plasma is typically an ionized gas, and is considered to be the fourth state of matter. "Ionized" in this case means that at least one electron has been dissociated from a proportion of the atoms or molecules. The free electric charges make the plasma electrically conductive so that it responds strongly to electromagnetic fields.

Plasma is usually formed by heating a gas until electrons can move freely. Ionization can also be caused by UV radiation, energetic particles, or strong electric fields.