Platinum plasma in our sputter system.  Plasma is the fourth state of matter (in addition to so

Platinum plasma in our sputter system. 

Plasma is the fourth state of matter (in addition to solids, liquids, and gases) that can be best described as an ionized gas.  It is a high energy state, in which there is sufficient energy to strip electrons from atoms or molecules in a gas.  The plasma glows because when the electrons recombine with atoms, energy is released in the form of light.  The color of the light depends on the composition of the plasma.  The plasma in this picture is purple mainly because of the argon ions used to bombard the platinum.

Surprisingly, even though plasma is probably one of the least known of the states of matter, it is the most common in the universe.  Examples of plasmas encountered in nature include lightning, some types of flames, nebulae, and stars.