Macrophage white blood cells. Transmission electron micrograph (TEM) of a section through two macrophages located within connective tissue, showing the nuclei and numerous lysosomes (dark spots). Lysosomes contain enzymes for digesting foreign particles. Macrophages are a type of large white blood cell that recognise foreign particles and phagocytose (engulf and digest) them. The slender finger-like extensions of the surface membrane able the macrophage to attach itself to its target. Magnification: x8300, when printed 10 centimetres wide.