Human fertilization is the union of a human egg in sperm, usually occurring in the amylla of the uterine tube. The result of this union is the production of a zygote or fertilized egg, initiating prenatal development. It's discovered the dynamics of human fertilization in the 19th century. The process of fertilization involves a sperm fusing with an ovum. The most common sequence begins with ejaculation during copulation, follows with ovulation, and finishes with fertilization. Various exceptions to this sequence are possible, including artificial insemination, in vitro fertilization, external ejaculation without copulation, or copulation shortly after ovulation. Upon encountering the secondary oocyte, the acrosome of the sperm produces, enzymes which allow it to burrow through the outer jelly coat of the egg. The sperm plasma then fuses with the egg's plasma membrane, the sperm head disconnects from its flag elum, and the egg travels down the phylope and tube to reach the uterus. In vitro fertilization is a process by which egg cells are fertilized by sperm outside the womb, in vitro. The sperm bind through the corona radiata, a layer of follicle cells, on the outside of the secondary oocyte, fertilization occurs when the nucleus of both a sperm and an egg fuse to form a diploid cell known as zygote, the successful fusion of gametes forms a new organism. Where the sperm at the zoon is about appears, the yolk is drawn out into a conical elevation, termed the cone of attraction or reception cone. As the sperm at the zoon has entered, the peripheral portion of the yolk change is into a membrane, the pair of the telene membrane, which prevents the passage of additional sperm at the zoon.