The gas that makes up about 78% of Earth's atmosphere is nitrogen. Nitrogen is a colorless, odorless gas that is essential for life, as it is a key component of amino acids, proteins, and nucleic acids, which are vital for biological processes. Although nitrogen is abundant in the atmosphere, it is relatively inert, meaning it does not readily react with other substances. Through the process of nitrogen fixation, some organisms, particularly certain bacteria, convert atmospheric nitrogen into a form that plants can absorb and utilize. This is crucial for the nitrogen cycle.