Nerve fibre. Comparison between a scanning election micrograph (SEM left) and transmission electron micrograph (TEM right) of a nerve, showing myelinated nerve fibres and a Schwann cell. Myelin (orange) is a fatty insulating sheath composed of schwann cells (pink with purple nucleus) that surrounds the axon and increases the speed of the nerve signal. Magnification: x10, 000 when printed 10 centimetres high. For a series of comparisons between SEMs and TEMs see images C047/7006 to C047/7034.