Nitrogen:
The most abundant gas; obtained by plants from bacteria in the soil, and obtained by people from the food they eat.
Besides creating up seventy-eight of the Earth's atmosphere, variety 7|chemical element|element|gas} features a number of uses. Since it's a gas, it is often used to replace air and cut back or eliminate reaction of materials.
The most necessary use is in making ammonia, that successively is employed to form plant food, explosives and alternative materials. Finally, N is employed as a refrigerant for terribly low temperatures.