A snowflake consists of roughly 1019 water molecules, which are added to its core at different rates and in different patterns, depending on the changing temperature and humidity within the atmosphere that the snowflake falls through on its way to the ground. As a result, it is extremely difficult to encounter two identical snowflakes. Initial attempts to find identical snowflakes by thousands their images under a from 1885 onward by found the wide variety of snowflakes we know about today. It is more likely that two snowflakes could become virtually identical if their environments were similar enough. Matching snow crystals were discovered in Wisconsin in 1988. The crystals were not flakes in the usual sense but rather hollow .
Snow crystals form when tiny cloud droplets (about 10 in diameter) . These droplets are able to remain liquid at temperatures lower than −18 (0 ), because to freeze, a few in the droplet need to get together by chance to form an arrangement similar to that in an ice lattice. Then the droplet freezes around this "nucleus". Experiments show that this "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than −35 °C (−31 °F). In warmer clouds an aerosol particle or "ice nucleus" must be present in (or in contact with) the droplet to act as a nucleus. Ice nuclei are very rare compared to that cloud condensation nuclei on which liquid droplets form. Clays, desert dust and biological particles may be effective, although to what extent is unclear. Artificial nuclei include particles of and , and these are used to stimulate precipitation in .
Tap on two or more of the same snowcrystals before they fall off the screen. Earn more than 250 points in one minute and you win. Sounds easy, doesn't it?