False-colour scanning electron micrograph (SEM) of a spreading macrophage, a phagocytic cell that is found in connective tissue and many of the major organs of the body. Macrophages belong to the reticuloendothelial system, as do monocytes, functioning to defend the body against invasion by foreign particles. In an active state, as here, the macrophage spreads out, using its frilly cytoplasm as limbs for movement & to engulf foreign material. Macrophages also function to process foreign (antigenic) substances for subsequent recognition & elimination by other white blood cells. Magnification: x1500 at 6x7cm size, x750 at 35mm size.