Sperm cells are equipped with a limited repertoire of behaviors that exclusively subserve their purpose to fertilize eggs (mature ova). When produced in the testis, sperm are immotile; they acquire the ability to swim as they transit through the epididymal tract of mammals or after ejaculation from invertebrates. But motility alone is not sufficient to direct a sperm to an egg. The egg itself (or associated structures) must “lure” the sperm by releasing diffusible chemotactic factors and/or through ligand/receptor interactions. After mammalian sperm become motile, they mature (a process called Capacitation) and are able to fertilize eggs within the female reproductive tract. Sperm and egg initially interact through surface receptors, and then the proteolytic contents of the sperm’s acrosomal vesicle [...]