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Light micrograph of a stellar plate snowflake. Snowflakes are symmetrical ice crystals that form inside clouds when water vapour condenses directly into ice. The exact shape of each snowflake depends on local climatic conditions within the precise area of the cloud where it is formed. As such, no two snowflakes are identical, with each individual pattern emerging as the crystal grows. The snowflakes were conserved in a thin layer of nail varnish and captured with differential interference contrast. Magnification 40x when printed at 10 centimetres wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/GERD GUENTHER/SCIENCE PHOTO LIBRARY)