This crystal measures roughly 0.85mm in diameter, and its part of a twin. The very center of the crystal is a hexagon growing on a higher "plane", and it's connected to the bottom by a central column.
You can see the snowflake was happy growing as a hexagon up until a certain point. The environmental conditions changed, likely higher levels of humidity or temperatures approaching -15C. These conditions are commonly associated with branching and rapid crystal growth. Because this happened right when the snowflake left the cloud, it could have been triggered during its descent. As it fell to a lower layer in the cloud, these environmental conditions could have been present, growing very small branches before the snowflake fell to Earth.
And it's already begun to melt. The tips are rounded, which shows that the crystal has either begun to melt or sublimate (evaporate from solid to gas). I'm sure this snowflake wouldn't have lasted more than an hour, even in extremely cold temperatures. It would disappear back into the thin air that created it. :)
If you like my snowflake work, check out my newly public 304pg hardcover book on the subject: http://skycrystals.ca/