Snowflakes have captured the human imagination since long before we understood their origins. Even before the invention of the microscope, just holding a snowflake up to your eye could let you see an incredible level of detail — and, it seems, the details were always different. Snowflakes have become a symbol of uniqueness, of the sheer level of variety possible, even within a simple and restrictive framework. People see, or try to see, something about human nature in the birth of such delicate and varied structures.

How could a simple, natural process give rise to that kind of variety? It would seem that a simple process like ice formation would play out fairly predictably, but it turns out that while we may know the basics of how snowflakes form, the random factors that influence their specific pattern are virtually unknowable. From flecks of dust to a passing currents of hot or cold air, there are all sorts of unpredictable factors that give rise to a snowflake’s particular conformation. There are, however, some generalities.