Color enhanced scanning electron micrograph (SEM) of erythrocytes, or red blood cells. Red blood cells are biconcave and highly elastic enabling them to pass through narrow capillary vessels. These erythrocytes distribute oxygen to the body, and carry the waste gas carbon dioxide back to the lungs. Each cell's interior is packed with hemoglobin, an iron rich pigment that has high oxygen carrying capacity. 2000x at 35mm