The main component of the air we breathe is nitrogen, which comprises about 78% of earth's atmosphere. Oxygen, the vital element for human and animal respiration, makes up roughly 21% of the atmosphere. Other gases present in smaller amounts include argon, carbon dioxide, and trace gases. Nitrogen is a relatively inert gas, meaning it doesn't readily react with other substances under standard conditions. It plays a critical role in the nitrogen cycle, which is essential for the growth of plants and the overall health of ecosystems.