The key milestones in the life and main scientific achievements of the famous Russian histologist Alexander A. Maksimov (January 22, 1874–December 3, 1928), a graduate and gold medalist of the Imperial Military Medical Academy, who headed its Histology Department with a course of embryology for 20 years, were studied (1903–1922). A.A. Maximov was born in St. Petersburg into a merchant family and spent his childhood years in Vasilyevsky Island. Some buildings where the A.A. Maximov family lived have survived to this day. A.A. Maximov had three older sisters: Vera, Evgenia, and Claudia. The gymnasium in which A.A. Maximov also studied in Vasilyevsky Island. The director of the educational institution (one of the best in St. Petersburg) was the famous teacher–organizer Karl I. May. The archives preserve information about the progress of Maximov’s essay, which testifies to his excellent studies. Maximov graduated with a gold medal. One of his classmates at the Imperial Military Medical Academy was Vladimir A. Oppel, who later became a famous surgeon. He left interesting memories of Maximov during the years of joint study at Imperial Military Medical Academy. While in exile, Maximov constantly remembered his homeland, colleagues, and native places where he spent most of his life. His works remain relevant today. Emphasis is placed on the key scientific developments of A.A. Maximov — unitary theory of hematopoiesis, identifying the morphological basis of inflammatory reactions, and neoplasm of connective tissue in experiment. The results of a search for previously unpublished St. Petersburg addresses related to the life of A.A. Maximov are presented. Based on recently discovered archival documents, new information is provided that complements the biography of the outstanding Russian histologist who pioneered the study of stem cells.