Because of the geometry of bonds between water molecules, snow flakes are all based on hexagons. Still, depending on temperature and humidity, the bonding can result in any number of shapes. But without a microscope, at the superficial level, they may look alike. Wang's actual excuse for studying frozen, airborne water is to figure out how it will affect global climate . Clouds, especially the high-flying cirrus clouds, are essentially formations of airborne ice, and they can have a complicated effect on the Earth's heat budget.
Clouds reflect some incoming sunlight back to space, but they also reflect heat back to Earth.
In other words, clouds could either amplify or dampen global warming. Wang says there are too many variables to know the correct answer, particularly since, as his graduate student Emily Liu just learned, the exact effect depends to some extent on the shape of the ice crystals.