Human sperm. Colored Scanning Electron Micrograph (SEM) of mature human sperm (also called spermatozoa). Sperm are the motile male sex cells produced in the testis. Each sperm is about 65 micrometers long and broadly divided into head (orange), neck and tail (yellow) regions. A pear-shaped head contains the nucleus and genetic material of the male needed to fertilize the female egg (ovum). The head is joined to the tail by a short neck. The sperm's tail enables it to swim by whiplash movements, an action that propels it to reach the ovum. Magnification: x2000 at 6x7cm size.