Liquid nitrogen is a substance that is in its liquid state at extremely low temperatures, typically below -196 degrees Celsius. It is made up of nitrogen gas which has been cooled and condensed into a liquid form. Liquid nitrogen is often used for various industrial applications such as freezing and preserving food products or in the production of semiconductor materials, among others. Due to its extremely low temperature, it can also be used to quickly cool down other substances or objects by direct contact.