Transmission electron micrograph of part of a macrophage cell. Some of the organelles inside the macrophage are visible here including mitochondria (the powerhouses of the cell responsible for making energy that the cell needs to function), golgi membrane stacks (play a role in transporting different molecules around the cell) and the edge of the nucleus (bottom left). Macrophages are white blood cells of the immune system which engulf and destroy foreign material. They are found in all tissues of the body. Width of image is 4.5 micrometres.