is a fundamental step in sexual reproduction in which the male gamete fuses with the female gamete to form the embryo, called the zygote. In humans, the sperm
plays the role of the male gamete and the egg
is the female gamete. The spermatozoa contained in the semen enters the woman's vagina
will come into contact with the egg, and one of them will penetrate the egg. After penetration, the oocyte will be "sealed" to the entry of other sperm, allowing the development of a single embryo. When fertilization cannot occur naturally, in vitro fertilization
can be practiced, which involves the formation of an embryo outside the woman's body, which is then transferred into her uterus.