Internal bleeding in lung tissue due to pulmonary emphysema, light micrograph. The bleeding is seen as numerous red blood cells (red). This bleeding resulted from the breakdown of the lung's smallest blood vessels (the pulmonary capillaries) during emphysema. Emphysema is a disorder where the tiny air sacs (alveoli) in the lungs become enlarged, and the walls separating them are damaged. This causes breathlessness and can eventually cause death. Magnification: x220 when printed 10cm wide.