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Snowflake. Light micrograph of a capped column 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. Capped columns first grow into stubby columns and then are blown into a region of the clouds where the growth becomes plate-like. This results in two thin plate-like crystals growing on the end of an ice column. (KEYSTONE/SCIENCE PHOTO LIBRARY/KENNETH LIBBRECHT/SCIENCE PHOTO LIBRARY)