Absolute Zero

Absolute zero is the theoretical coldest temperature thought to exist. At absolute zero, the movement of all atoms stops. Although scientists have simulated temperatures within trillionths of a degree of it, reaching absolute zero is currently believed to be impossible.Smithsonian Magazine: The Coldest Place in the Universe (January, 2008)

At temperatures very close to absolute zero atoms move so slowly that they become another state of matter other than solid, liquid or gas. This form of matter is called a Bose-Einstein Condensate. Bose-Einstein Condensate has unique properties including the ability to slow down or stop light in its path.Smithsonian Magazine: The Coldest Place in the Universe (January, 2008)