Light micrograph of human blood cells, showing numerous red cells (erythrocytes) and a single neutrophil (white cell). The pink-staining erythrocytes are biconcave discs packed with haemoglobin that act as carriers of oxygen and carbon dioxide to & from tissues. Mature erythrocytes possess no nucleus or other organelles; these are lost during maturity. The main function of neutrophils is to engulf invading microorganisms, particularly bacteria. Neutrophils are the main type of white cells involved in acute inflammatory responses. Their most prominent features are multi-lobed nuclei. Magnification: x100 at 35mm size.