Gustaf Retzius (1842-1919) dedicated a large part of his life to researching the histology of the sense organs and nervous system. He was first awarded a professorship in histology at KI, and then a few years later also became a professor of anatomy. Gustaf Retzius published more than 300 scientific works in anatomy, embryology, anthropology, zoology and botany. He gave his name to the millimeter-large Retzius cells in the central nervous system of the leech (Hirudo medicinalis). He was also a journalist, the editor of newspaper Aftonbladet (1884-87), and married to Anna Hierta, daughter of Aftonbladet's founder Lars Johan Hierta.

Gustaf Retzius was politically a liberal and socially active. Together with his wife he founded the Hierta-Retzius foundation, which is now administered by the Royal Swedish Academy of Sciences. The foundation has two funds, one for the promotion of biological research the other for supporting projects of an important scientific or social nature. In 1901 Gustaf Retzius became a member of the Swedish Academy.