The male and female reproductive systems are designed to create life. Deep inside the woman, in her ovaries, one egg develops each month. From the man\'s testes, through his penis, millions of sperm enter the woman\'s vagina. Here, they begin their travel toward the egg. Only one sperm can enter an egg. When one does, fertilization occurs. Genetic material from the male and from the female combine, to create the first cell of an offspring. The fertilized egg migrates to the uterus where it develops into a fully formed fetus over a period of about 40 weeks. Then, a baby is born.