He was the first scientist to produce photomicrographs of the tubercule bacillus. The photomicrographs in the paper reveal an organism morphologically identical to that seen now. From over 3,000 photomicrographs he established a general classification of natural snow crystals. Until very recently, photomicrographs were expensive to reproduce. Photomicrographs obtained by SEM showed that the smear layer consists of two confluent components.