The gas most commonly found in the atmosphere is nitrogen. Comprising roughly 78% of Earth's atmosphere, nitrogen is a colorless, odorless gas essential for life. It is a key component of amino acids, proteins, and nucleic acids, contributing to the formation of living organisms. While nitrogen itself is not directly usable by most organisms, it is converted into forms that can be utilized, such as ammonia, through biological processes like nitrogen fixation. The remaining components of the atmosphere include oxygen (about 21%) and trace amounts of other gases, with nitrogen playing a crucial role in maintaining the balance necessary for life.