Every breath you take is a complex, life-sustaining process powered by your lungs. These vital organs work nonstop to bring oxygen into your body and remove carbon dioxide, a waste gas. As you inhale, air travels through your nose or mouth, down the trachea, and into the bronchi—branching tubes that lead to each lung. Inside the lungs, millions of tiny air sacs called alveoli exchange gases with your bloodstream. This oxygen fuels every cell, while carbon dioxide is expelled when you exhale.