Johannes Holtfreter (January 9, 1901 – November 13, 1992)[1] was a German-American developmental biologist whose primary focus was the “organizer,” a part of the embryo essential for the development of the proper body plan.

[3] As a child, he captured animals (including butterflies) and made drawings of them, and after graduating from the Realgymnasium, he wanted to enter field biology.

After obtaining his Ph.D. in 1924, he eventually entered the field of marine biology at the Stazione Zoologica in Naples, and traveled around Europe afterward, painting, attempting to research, and passing through locations including Lapland and Helgoland.

Through his research on amphibian embryos, Holtfreter had made many significant discoveries in the field of developmental biology, though the organizer or neural inducer was his major focus.

[6] Holtfreter also solved two problems that plagued many other preceding developmental biologists (infection of embryo specimens by bacteria and inability of the specimen to survive in solutions containing improper levels of salts) by devising both the sterile technique to eliminate bacteria and Holtfreter's medium to allow the developing embryonic cells to survive for extended periods.