Macrophage. Coloured transmission electron micrograph (TEM) of part of a macrophage from a degenerating nerve. Large amounts of engulfed myelin debris is present (brown). Large number of stacked smooth endoplasmic reticulum of golgi bodies are also visible. Macrophages are a type of large white blood cell that are found in tissues rather than circulating in the blood. They recognise foreign particles, including bacteria, pollen and dust, and phagocytose (engulf) and digest them. Magnification: x3000 when printed 10 centimetres wide.