Made by: Freezing
Ice crystals grow normally in certain given directions as determined by the internal hexagonal ice symmetry. These directions can be seen particularly in the so-called dendritic snow crystals with six ”arms”. When the air is relatively dry and the ground very cold, a pattern which reminds of snow crystals occurs, while humid air promotes feather-like shapes
I find it interesting that different temperatures and air humidity can achieve such beautiful patterns; arbitrary and at the same time so perfect and measured.