Fertilization results in the formation of a zygote which begins to develop into an embryo.
During gestation, human embryos develop a distinctive tail. On the other hand, these are mere relics and are gone after birth. Gestation is the period of time between conception and birth.
The tail of a human embryo is about one-sixth the size of the embryo.
A normal human embryo has 10 -12 growing tail vertebrae when it is between 4 and 5 weeks old.
The tail of a human in embryos disappears after eight weeks.