Lung bronchiole, coloured scanning electron micrograph (SEM). This slice through the tissue has formed a cross-section across the bronchiole, one of the types of branching airways found in the lungs. Red blood cells (red, erythrocytes) are visible. The lungs are where gas exchange (in the alveoli) takes place between the air and the red blood cells. This brings oxygen to the body and releases the respiration waste product carbon dioxide.