Reevaluates Nicolaus Steno’s contributions to anatomy and early modern science, examining his interdisciplinary interests in their historical context.   Nicolaus Steno (1638–1686) was a renowned anatomist in his lifetime. He reformed the anatomical understanding of glands, argued that the heart was a muscle, renamed the so-called female testicles as ovaries, and developed a mathematical model for understanding muscle contraction—discoveries that were fundamental to the fields of anatomy and physiology. However, other aspects of Steno’s life have come to define him: his claim that mountains’ strata reveal the history of the Earth and his conversion to Catholicism as a practicing scientist. This excessive attention to his geological discoveries and to asking whether science and religion are compatible, Nuno Castel-Branco argues, has obscured his significant accomplishments as an anatomist. The Traveling Anatomist thus restores Steno to his rightful place as a crucial figure in early modern science.   Using Steno’s extensive travels as a framework, this book depicts him as an active participant in the Republic of Letters. Castel-Branco traverses Leiden, Paris, Copenhagen, Florence, and Rome as he follows Steno in his sojourns through different scientific academies, courts, and artisanal workshops. There he developed new friends, some of whom were women, with whom he researched and exchanged ideas. Drawing on Steno’s books, correspondence, and novel archival material, Castel-Branco invites us to approach Steno and his accomplishments in anatomy, mathematics, and geology through the eyes of his contemporaries. Doing so, Castel-Branco reconstructs the rich and overlapping worlds of scientific disciplines that shaped Steno’s work, revealing the richness of interdisciplinary research in early modern intellectual life. And through Steno, he illustrates larger developments and new networks of significance in mid-seventeenth-century science. By focusing on ideas, scientific genres, institutions, and friendships, Castel-Branco offers a way others might also productively study science from the early modern period until today.