Three lower energy phases of matter are solid, liquid, and gas. Plasmas are the most common form of matter, comprising more than 99% of the visible universe. Everyday forms of plasma are the sun and stars, which are plasmas heated by nuclear fusion, fluorescent and neon lights, lightning?, the [Aurora borealis]?, solar wind, and interstellar nebulae
Sir William Crookes, an English physicist, identified a fourth state of matter, now called plasma, in 1879. The word 'plasma' was first applied to ionized gas by Dr. Irving Langmuir, an American chemist and physicist, in 1929.
See plasma physics for active research topics.
See also [Life sciences]?[blood plasma]?