Liquid nitrogen: Nitrogen in a liquid state. Liquid nitrogen is supercool -- about 200 degrees Celsius (320 degrees Fahrenheit) below zero -- and is used for cryopreservation, cryosurgery, and cryomedicine.
Liquid nitrogen is invaluable for preserving blood and bone marrow cells, sperm, ova, early embryos, and, in the microbiology laboratory, a variety of microorganisms (bacteria, fungi, etc). In cryosurgery, a super-chilled scalpel may be used to remove cancer tissue.
In dermatology, liquid nitrogen is commonly used to freeze benign growths, precancers, and skin cancers. The liquid nitrogen is usually applied by a spray bottle (canister) or a cotton swab. It is the thawing process that damages the cells. Liquid nitrogen is also known as LN2.