Oxygen is the gas essential for humans to breathe. It is vital for the process of cellular respiration, where cells convert nutrients into energy. Our bodies rely on oxygen to sustain life, as every organ and tissue needs this gas to perform its functions. Humans inhale oxygen from the atmosphere, and through the lungs, it enters the bloodstream and is transported to cells throughout the body. The process of breathing, or respiration, is critical for maintaining the balance of oxygen and carbon dioxide levels, which is necessary for overall health and survival.