The element essential for respiration in humans is oxygen. Oxygen is critical for cellular respiration, a process that generates energy in the form of adenosine triphosphate (ATP) by oxidizing nutrients in the presence of oxygen. This process primarily occurs in the mitochondria of cells. Breathing brings oxygen into the lungs, from where it is absorbed into the bloodstream and transported to cells throughout the body. Oxygen is vital for the survival of aerobic organisms, as it supports the metabolic processes necessary for growth, reproduction, and overall cellular function. Without oxygen, cells cannot function effectively, leading to serious health consequences.