Sperm is a sex cell or “gamete.” Sperm cells carry half of the chromosomes, or genetic information, for the potential offspring. When a sperm cell fertilizes an egg, they join chromosomes, making an organism with a unique genetic combination. This is why you inherit some traits from each of your parents.
Sperm cells are approximately 0.05 milliliters long (about 0.002 inches). They’re not visible to the naked eye, but using a microscope, we can see the structure of sperm. They have a few distinct parts: the head, which contains the nucleus where genetic material is carried; a midpiece; and a tail, which propels it for swimming and helps breach the egg.
Learn more in our sperm overview.