of snow crystals, classifying them into seven major and numerous minor types. In the course of these observations, taking photographs of natural snow and sorting them by appearance according to weather conditions, Nakaya felt the need to make artificial snow from ice crystals grown in the laboratory. He generated water vapor in a dual-layer hollow glass tube, which was then cooled. Contrary to his initial expectations, creating snow crystals was not an easy task – instead of forming into snowflakes, the ice crystals grew like caterpillars on the cotton string he used for nucleation. The Low Temperature Science Laboratory opened in 1935, and experiments continued with various materials for the ice nucleus. These experiments revealed that woolen string is better than cotton string; however, the snow crystals were still not forming as intended. One day Nakaya found a snow crystal on the tip of a hair of a rabbit-fur coat in the lab. This was the breakthrough that led to the production of the first artificial snow crystal. On March 12, 1936, three years after the first attempt, he produced a snow crystal on the tip of a single hair of rabbit fur in his laboratory apparatus. In December 1937, he took photographs of many types of artificial snow crystals in his lab. Such photographs, collected in Bentley's book Snow Crystals, which Nakaya admired greatly, later influenced Nakaya's own work. Nakaya continued his research into snow crystals and elucidated how their various patterns are produced in nature. He published his Nakaya Diagram, which describes the relationships among vapor, temperature, supersaturation, and excess vapor density in clouds. Nakaya's achievement is commemorated today by a hexagonal stone monument at the site of his laboratory on the campus of Hokkaido University. His original apparatus is preserved and on display at The Institute for Low Temperature Science. Essays on science Nakaya was also a prolific science essayist. A select bibliography at the website of the Nakaya Ukichiro Museum of Snow and Ice lists more than 40 titles that explained science for the general public, on topics ranging from snow and geophysics to archaeology and the scientific method. He also produced a number of documentary films and radio programs. In 1950, he played a central role in the founding of Iwanami Productions, which went on to produce more than 4,000 documentary and educational films. (The films are now available from Hitachi Media Productions in digital