Plasma is the energy rich fourth state of matter in which a gas contains an electrically neutral medium of electrons and ions. Any energized gas can form plasma, but the surface effects will be very different, depending on the nature of the gas and the desired results. Similar to a gas, plasma does not have a definite shape or volume. Believe it or not, plasma is the most common form of matter in our universe. Some common forms of plasma include stars and neon signs.