The gas most abundant in Earth's atmosphere is nitrogen, comprising about 78% of the atmosphere by volume. It is a colorless, odorless gas that plays a crucial role in various biological processes, particularly in the nitrogen cycle. Nitrogen is essential for the synthesis of amino acids and nucleotides, which are the building blocks of proteins and DNA. While it is inert in its gaseous form, nitrogen can be transformed into reactive compounds through processes like fixation, allowing it to be utilized by living organisms. Its abundance and stability contribute to the overall composition and balance of Earth's atmosphere.