Sperm cells, or spermatozoa, are the male reproductive cells in many organisms, including humans. They are produced in the testes through a process called spermatogenesis. Each sperm cell has a head, which contains genetic material, a midpiece that provides energy, and a tail, or flagellum, that helps it swim toward the egg. The primary function of sperm cells is to fertilize the female reproductive cell, known as the ovum. During sexual reproduction, a sperm cell must travel through the female reproductive tract to reach and penetrate the ovum, leading to the formation of a zygote and the beginning of a new organism.