Respiration is the process by which living organisms convert food into energy. This happens in two main stages: external respiration, where oxygen is taken in and carbon dioxide is released, and internal respiration, where oxygen is used to break down glucose for energy. This energy is essential for all bodily functions, from moving muscles to thinking. In humans, respiration primarily occurs in the lungs. When we breathe in, oxygen enters the lungs and travels to the bloodstream. At the same time, carbon dioxide, a waste product, is expelled when we breathe out. This exchange keeps our cells energized and functioning properly.