Book excerpt: Propagating life to the next generation is a hormone-dependent process relying on the individual wish to generate own progeny and resulting in maintenance of species. Follicle-Stimulating Hormone (FSH) is a key reproductive hormone in vertebrates used as a drug in the treatment of human infertility and hypogonadism. The FSH-FSH receptor system began to be characterized in its essential functioning mechanism only in the last couple of decades, i.e. long after the clinical use of the hormone. Some novel, intriguing aspects of FSH function are now emerging, This eBook contains the most recent scientific advances about FSH and its receptor, contributed by the world leaders of the field.