Cryogenics processes differ based upon what is being cooled down and the intended effect, but they always utilize very low temperatures, often contained within chambers. Cryogenics deals with a wide range of materials, from biological tissue to inorganic metals and gases, necessitating a wide range of processes.
Cryogenics, in general, refers to the field that studies, utilizes and experiments with materials under very cold temperatures. However, colloquially, it often refers to medical procedures that use cold temperatures to heal or preserve the human body. The life-extension technique is more properly called cryonics. Cryogenic experts consider this particular application untenable, although cryogenics does have some scientifically verified medical uses.
In cryogenic medical procedures intended to preserve tissue, a solution containing chemical preservatives is used to induce vitrification, a state that allows cells to be brought to a very low temperature without the formation of ice crystals. Under normal circumstances, ice crystals cause damage when cells are cooled down significantly.
Another cryogenic process, cryotherapy, intentionally damages tissue to destroy potentially dangerous abnormal cells. Very cold gas is rapidly applied to a small part of the body using a tubular cryoprobe. As of 2015, this is a common treatment for cervical dysplasia.
In the manufacturing industry, cryogenic processes are also used to treat metal, especially steel. Procedures that successively cool and heat steel produce particular crystal structures within the alloy. These structures have desirable traits, like increased durability. Metallic cryogenic processing of steel uses liquid nitrogen to cool steel to -300 degrees Fahrenheit after the steel has already undergone high temperature processing. An even greater temperature differential can be achieved using liquid helium, cooling the steel to -400 degrees Fahrenheit.