Human fertilization is a complex, highly regulated process that involves intricate molecular interactions between sperm and egg. Ultimately, this process culminates in the fusion of the gamete membranes to form a zygote. Gene disruption studies in mice have identified several critical fertilization factors. This SnapShot highlights the structure function of key proteins at the sperm-egg interface, providing insights into the mechanism of fertilization. To view this SnapShot, open or download the PDF.