The state of the union: the cell biology of fertilization

Fertilization is the process by which sperm and egg unite. An expanded understanding of the mechanisms that underlie these events has provided insights into an important aspect of early development and also has proven to be a valuable model in which to study cellular function. In addition, many emerging strategies for contraception and for the treatment of infertility are based on the mechanism of gamete interaction. Here, we discuss the cell and molecular biology of mammalian fertilization, highlight selected recent breakthroughs and attempt to identify key unanswered questions.