A critical biography of the early modern Italian naturalist. The Bolognese naturalist Ulisse Aldrovandi was a prolific writer, learned polymath, and prodigious collector who amassed the largest collection of animal sex organs and illustrations in sixteenth-century Europe. This book provides a concise yet comprehensive portrait of Aldrovandi, paying particular attention to how the discovery of the New World influenced his research into physiological abnormalities. Cutting a cogent path through the latest research, Peter Mason sheds new light on Aldrovandi's fascinating life, his early forays into natural history, his network of correspondents and patrons, and his work's ongoing legacy today.