Sometimes called “the fourth state of matter,” plasma is one of the four fundamental forms of matter that commonly exist. The other three are solid, liquid and gas. 
Plasma contains ions, free radicals, neutral byproducts, and photons. Plasma can be created by heating a gas or subjecting it to a strong electromagnetic field. This decreases or increases the number of electrons, creating positively or negatively charged atoms or molecules called “ions.”
With plasma, positively charged nuclei swim in a “sea” of freely-moving disassociated electrons, similar to the way such charges exist in conductive metal. This electron “sea” allows matter in the plasma state to conduct electricity.
Like a gas, plasma does not have definite shape or volume. Unlike gases, however, plasmas are electrically conductive, produce magnetic fields and electric currents, and respond strongly to electromagnetic forces.
The plasma state, although less understood, is quite common. Lightning, electric sparks, fluorescent lights, neon lights, plasma televisions and some types of flame are all examples of illuminated matter in the plasma state.
