Animal embryos are stored in liquid nitrogen. Some people have even paid for their bodies to be frozen in liquid nitrogen after they die, in case one day a way is found to bring them back to life. Some fish cannot survive in acid waters. The average person contains almost 2kg of proteins. Your skin, your hair, and your fingernails, are all made from proteins.
All proteins contain nitrogen.
The atomic number for nitrogen is 7. Nitrogen is found in the air. If you cool nitrogen gas down, it becomes liquid at minus 195 degrees Celsius. This is much colder than, for example, water vapour, or steam, which becomes liquid at plus 100 degrees Celsius, when you cool it down. The temperature at at which a substance becomes liquid when you cool it down, is the temperature at which it boils when you heat it up.