The element essential for breathing is oxygen. Oxygen is a colorless, odorless gas that constitutes approximately 21% of Earth’s atmosphere. It is crucial for the survival of most living organisms, as it is required for cellular respiration, a process in which cells convert nutrients into energy. Humans and animals obtain oxygen through the lungs, while plants produce oxygen as a byproduct of photosynthesis. Oxygen's role in sustaining life cannot be overstated; it is vital for metabolism and energy production in cells. Without sufficient oxygen, living organisms cannot survive, highlighting its significance in ecosystems worldwide.