The materials within The Johannes Holtfreter Papers are from the professional life of Johannes Holtfreter, who was a prominent developmental embryologist in the mid-1900s. Within the collection are series of correspondence, experiment notes, experiment illustrations, photographs, and movie film. This collection documents Dr. Holtfreter’s work with the Spemann-Mangold’s Organizer, his work with amphibian embryo development, and his collaborations with fellow embryologist Viktor Hamburger.