Relaxin, perhaps more than any other hormone, has a varied history of eliciting enthusiasm, rejection, skepticism, and long lapses of neglect. Long after its discovery, it was a hormone in search of a physiological role in humans. Today, relaxin is implicated in mammary growth, development and function, ionotropic and chronotropic action on the heart, and angiogenic activity in both the peripheral tissues and the endometrium. It is best known for its effect on the uterus and the symphysis pubis in preparation for parturition. However, the literature suggests that not all functions occur in one species. This book describes how to obtain the necessary molecules or derivatives for research, reaching right into the design of new molecules for specific applications.