The process of conception is calculated from the time the sperm combines with the egg to form a zygote. Until the embryo is formed and nested in the uterus. After fertilization for about 3-4 days, the egg is fertilized. That is, the zygote begins to gradually move into the uterus to find a place to nest and divides 3 times along the way. After the egg meets the sperm to form a zygote and moves to nest in the uterus, life begins with changes from some initial cells to form a complete body. So when does the embryo appear? How does the embryo develop?