Sperm cells are the part of the semen with which a man can father a child. All that needs to happen is the fusion between a sperm and an egg cell.
The head contains the nucleus with DNA, the hereditary properties, while the tail makes the sperm move.
Every night the male body produces 72 million sperm cells. One is enough to father a child. If you put all the sperm cells responsible for the people that live today together they would fit into one thimble.
Sperm is made in the testis, which takes 72 days. When they are complete they move to the epididymes,
where they learn to swim in about 12 days and are stored.
Sperm cells which enter a girl’s body with intercourse can remain active for days, even a week.