Sperm cells.. Comparison between a scanning election micrograph (SEM left) and transmission electron micrograph (TEM right) of sperm cells. In the TEM image the heads of the sperm, which contain the genetic material, are bottom and right (red). The central part of the cells contains mitochondria and provides the energy for the cell, (round, larger). The ends of the tails are the smallest round structures. The tail's motility is aided by the arrangement of microtubules (part of the cell cytoskeleton) within the tail. The microtubules are arranged in a central axoneme, with a central pair of microtubules surrounded by nine other pairs in a ring. Magnification: SEM x 3000, TEM x10, 000 when printed 10 centimetres high. For a series of comparisons between SEMs and TEMs see images C047/7006 to C047/7034.