Nature The Sculptor: Science of Snowflakes
Just as with raindrops, a snowflake begins as a droplet of water which condenses on a speck of dust. The droplet freezes and more droplets condense and freeze on it (remember how ice will stick to your tongue?) If the cloud temperature stays below freezing, enough droplets will freeze and collect to form a snowflake. Because of the way water molecules fit together, most snowflakes are six-sided (hexagonal.) When the snowflake gets heavy enough, it descends to Earth.