The term cryogenics comes from the Greek word kruos , for "frost." The subject deals with the properties of matter at very low temperatures, close to absolute zero (-273° C or 0° K) as well as with the equipment and processes by which such temperatures can be attained. The science of cryogenics is closely related to the commercial process of refrigeration, and progress in one field is often the result of progress in the other.

The origin of cryogenic research is often association with the first liquefaction of oxygen, nitrogen, and carbon monoxide gas by the French physicist, Louis Paul Cailletet, in 1877. Cailletet's work was closely paralleled by that of the Swiss chemist, Raoul Pierre Pictet. Cailletet and Pictet--as well as all early cryogenic researchers--used the Joule-Thomson effect to attain low temperatures. The first step in using the Joule-Thomson effect is to cool and compress a gas as...