What an interesting question! We hope this simplified answer helps! Here goes... When water molecules freeze, they turn to ice. Ice molecules are crystals. Crystals are little boxes with flat sides, that can be many different shapes ... ice crystals are shaped like tiny rectangular boxes, like this: Ice crystals like this can join together to make BIGGER crystals ... but only matching sides can join up! For example, a left and a right side can join up with two other ice crystals like this: Similarly, ice crystals can join at the top or bottom, like this: Now you would have a bigger ice crystal, or 'snowflake', that would look like: But ice crystals can also join on the front and back, this way ... See what happens? Because more ice crystals can join together on six sides of the original ice crystal, what you get is a six-legged gigantic ice crystal! We call these snowflakes. Resources