Cryogenics
study of the production and behaviour of materials at very low temperatures
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a universal definition of "cryogenics" and "cryogenic" by accepting a threshold of 120 K (−153.15 °C) to distinguish these terms from conventional refrigeration. This is a logical dividing line, since the normal boiling points of the so-called permanent gases (such as helium, hydrogen, neon, nitrogen, oxygen, and normal air) lie below 120 K, while the Freon refrigerants, hydrocarbons, and other common refrigerants have boiling points above 120 K.
Discovery of superconducting materials with critical temperatures significantly above the boiling point of nitrogen has provided new interest in reliable, low-cost methods of producing high-temperature cryogenic refrigeration. The term "high temperature cryogenic" describes temperatures ranging from above the boiling point of liquid nitrogen, −195.79 °C (77.36 K; −320.42 °F), up to −50 °C (223 K; −58 °F). The discovery of superconductive properties is first attributed to Heike Kamerlingh Onnes on 10 July 1908, after they were able to reach a temperature of 2 K. These first superconductive properties were observed in mercury at a temperature of 4.2 K.
Cryogenicists use the Kelvin or Rankine temperature scale, both of which measure from absolute zero, rather than more usual scales such as Celsius which measures from the freezing point of water at sea level or Fahrenheit which measures from the freezing point of a particular brine solution at sea level.
Definitions and distinctions
Cryogenics
The branches of engineering that involve the study of very low temperatures (ultra low temperature i.e. below 123 K), how to produce them, and how materials behave at those temperatures.
Cryobiology
The branch of biology involving the study of the effects of low temperatures on organisms (most often for the purpose of achieving cryopreservation). Other applications include Lyophilization (freeze-drying) of pharmaceutical components and medicine.
Cryoconservation of animal genetic resources
The conservation of genetic material with the intention of conserving a breed.
Begin with the source’s own compact description: “Cryogenics” is study of the production and behaviour of materials at very low temperatures. The dossier treats that line as a proposition to test through Cryogenics, study and production, not as a finished interpretation.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Jun 25, 2026. The linked authority identifier is Q192116. The Library of Congress control number is sh85078650. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 1971 and 1908.
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