Five kinds of snow crystals are simple prisms, stellar plates, stellar dendrites, sectored plates and rimed crystals. Snowflakes are formed when water vapor freezes in clouds then falls through cold air to the ground. Snowflakes are almost always six-sided.
The six-sided prism is the basic snowflake. These prisms can be plates, columns, button-like or resembling nuts for construction. They are often faceted and so tiny that they need magnification to be properly seen.
Stellar plates are star-shaped, very thin and faced with symmetrical designs. They usually occur when the temperature is just below freezing or very cold. Stellar dendrites are much like stellar plates but have tree-like twigs and branches. These are large snowflakes and are the inspiration for the familiar snowflake design. Sectored plates are also stellar plates but with pronounced ridges.
Rimed crystals occur when the water droplets that float around the snow cloud stick to snowflakes and freeze. When this happens, the droplets are known as rime. Every type of snowflake can be encrusted with rime. When many droplets adhere to a snowflake to the point where it looks like a snowball, the object is called graupel. Sometimes, the snowflake looks like a star or hexagon covered with tiny bubbles.