Historians of medicine and generation have long demonstrated how the female body was conceptualized as a site of secrecy in early modern Europe. This essay explores one oft-overlooked organ of the female body—the placenta, which was considered by early modern anatomists to be a particularly challenging secret to uncover. Anatomists who investigated this organ discovered that it was largely absent from the ancients’ accounts of their knowledge of generation, and their own studies of its structure and function revealed a complexity difficult to understand. Through an analysis of anatomical treatises and midwifery guides, this essay investigates how textual and visual knowledge about the placenta was produced and shared by anatomists, medical practitioners, and female midwives. It argues that the secrets of the placenta presented a lucrative opportunity for anatomists to expand their intellectual and financial riches. The study provides fresh insights for historians of science, medicine, and gender and new perspectives on the history of reproduction and embryology.