During intercourse ,matured sperm cells ejaculated into the vagina, then transforted through the cervix or a part of the uterus. The uterus contracts until the sperm cells reach the matured egg cell at the uterine tubes or fallopian tubes where the fertilization occurs. Fertilization is the union of matured sperm cell and matured egg cells. When the egg cell and sperm cell meets, they will become one which called zygote. Zygote will undergo cell division within 18-36 hours, the zygote divides into many cells until it reach 12-16 cells after 2 or 3 days which called morula or the embryo. It will undergo cell division again until it develops a mass of cells which called BLASTOCYST. After day 6 at day 7 or 8 after ovulation, the uterine wall begin to thickened preparing for the implantation of the blastocyst, implantation occurs when the blastocyst attacher to the uterine wall, in this process the placenta begim to develop, placenta is where the unbilical cord connected to get nourish the fetus inside the womb of the mother. After implantation new cavity forms inside the innercell mass. The amniotic cavity is bounded by a membrane called AMNIOTIC SAC filled with AMNIOTIC fluid. The embryo grows inside the amniotic cavity, where the amniotic fluid serves as a cushion, while the embryo is inside the amniotic cavity the development of the body parts of the fetus undergoes from head to toe, it starts from the head particularly the nervous system. During second to 8th hours of development major organs appear and begin to develop. This stage called ORGANOGENESIS. The embryo becomes fetus for about 8 weeks. Begging of fetal period bone ossification begins with organ systems enlarge and mature the fetus grows on average from about 3cm and 2.5g at 8 weeks to 50cm and 3,300 g (7lbs, 402) at the end of pregnancy.