Oxygen

Oxygen is a colorless, odorless gas that makes up about 21% of Earth's atmosphere. It’s essential for most living organisms because it allows cells to produce energy through a process called respiration. When we breathe in, oxygen enters our lungs and then moves into our bloodstream, where it’s carried to cells throughout the body. There, it helps convert nutrients into energy, supporting vital functions. Oxygen is also involved in combustion and is used in medical treatments to help patients with breathing difficulties. Without oxygen, most life forms on Earth could not survive.