Alveoli are tiny air sacs located in the lungs that play a crucial role in breathing. They are the final destination for air we inhale, where oxygen from the air passes into the blood. Each alveolus is surrounded by a network of tiny blood vessels called capillaries, which help transport oxygen to the rest of the body. These small structures are essential for gas exchange, allowing carbon dioxide, a waste product, to be expelled from the blood. The large surface area of the alveoli, combined with their thin walls, makes them highly efficient for this process, ensuring our bodies receive the oxygen needed to function properly.