When there's a lot of snow out there, you can either make a snowman, a snow angel, or just X-ray the snowflakes. And if you do the latter, you can figure out how many different designs snowflakes take. Chemistry teacher and blogger Andy Brunning has created this graphic, which categorizes these designs into 39 different types, Smithsonian reports. Based on Japanese research, Brunning's graphic logs 35 flakes and a combo of sleet, ice, hail, and a hydrometeor particle rounding out the rest. Though it doesn't confirm every snowflake is unique, the 39 categories have a pretty impressive 121 more subtypes. The variety depends on temperature and humidity, Brunning writes on his blog—low humidity creates simpler shapes, while high humidity create more complex ones.
A fellow scientist at Caltech offers this poetic description for the snowflake's creation: "The story begins in a cloud," he writes, when a droplet turns to ice. The ice turns into a prism and grows branches from its six corners, then is "blown to and fro inside the clouds." Temperature changes then "morph the arms into different shapes and give us the diverse snowflakes and crystals we see." In the field of crystallography, scientists study these designs by passing X-rays through the flake. The design is simply an arrangement of atoms and the X-ray is diffracted as it passes through them; the diffraction pattern reveals the design, Brunning explains. For remarkable images of snowflakes, click here. (The East Antarctic Plateau probably has the simplest snowflakes on Earth.)