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Frost patterns, photographed by Wilson Bentley. Early gelatin silver print of frost patterns imaged by US photographer Wilson Alwyn Bentley (1865-1931), one of the first people to photograph snowflakes. Bentley attached a microscope to his camera and perfected a technique that allowed him to photograph snowflakes, frost and other ice phenomena before they melted. Frost forms when the temperature of a surface falls to below the freezing point of water, and water vapour in the air freezes onto the surface. Bentley's book 'Snow Crystals' was published in 1931. This photograph dates from around 1910. (KEYSTONE/SCIENCE PHOTO LIBRARY/METROPOLITAN MUSEUM OF ART/SCIENCE PHOTO LIBRARY)