I'm going to assume it has to do with the crystalline structure of ice. Crystals like to have a very specific structure, so there's only a few particular ways f

I'm going to assume it has to do with the crystalline structure of ice. Crystals like to have a very specific structure, so there's only a few particular ways for it to grow from a given point. For instance, the three-plane symmetry is going to be due to the hexagonal shape of ice crystals [0]. That's also going to inform how branches of branches are formed; note that secondary branches are all parallel to the sides of the entire hexagonal structure of the flake [1]. [0] https://en.wikipedia.org/wiki/Ice_crystals#Geometry https://en.wikipedia.org/wiki/Ice_crystals#Geometry [1] http://static01.nyt.com/images/2016/01/22/science/22Snowflake3/22Snowflake3-superJumbo.jpg http://static01.nyt.com/images/2016/01/22/science/22Snowflak...