A snowflake is a snow or ice crystal, most often in the form of a six-pointed crystal at the ends of stars or hexagonal plates. There are several snowflake symbols in Unicode: (U + 2744), (U + 2745), (U + 2746)
During very hard frosts (at temperatures below -30 ° C), ice crystals fall out in the form of "diamond dust" - in this case, a layer of very fluffy snow is formed on the surface of the earth, consisting of thin ice needles. Usually, in the course of its movement inside the ice cloud, ice crystals grow due to the direct transition of water vapor to the solid phase. How exactly this growth occurs depends on the external conditions, in particular, on temperature and air humidity. The nature of the dependence of scientists in general revealed, but to explain it so far could not. Under some conditions, ice hexagons are strongly growing along its axis, and then elongated snowflakes are formed - snowflakes-columns, snowflakes-needles. In other conditions, hexagons grow mainly in directions perpendicular to their axis, and then snowflakes form in the form of hexagonal plates or hexagonal asterisks. A droplet of water may freeze a falling snowflake - as a result, irregularly shaped snowflakes are formed.
Macro photos of snowflakes by a Russian photographer Alexei Klyatov.