Heinrich Tonnies (1825-1903) was born in Germany and trained as a glass painter and cutter. In a career shift, he acquired a fully equipped photography studio of C. Fritsche in Aalborg, Denmark. Under Fritsche's tutelage, Tonnies learned the craft. He eventually specialized in Cartes de visite photographs, which were small 2.5 x 3.5 inch albumen prints mounted on cards. Inexpensive to produce and pocket-sized, Cartes de visites became hugely popular around the world. For the general public, they traded like baseball cards creating “cardomania” fever. He photographed over 75,000 individual portraits during his career. Most Cartes de visites made by other photographers at the time were quite standard family portraits and vernacular pictures. But Tonnies operated on a higher level.