A snowflake is a tiny crystal of ice that falls from clouds as snow. Each snowflake forms when water vapor freezes around a speck of dust high in the atmosphere. As it tumbles through the clouds, it grows into delicate, six-sided patterns. Scientists have photographed millions of snowflakes and found that each one has a unique shape, though they all share that basic six-sided structure. This happens because of how water molecules bond together as they freeze. When you catch a snowflake on your mitten and look closely before it melts, you might see its intricate branching design, like nature's tiniest work of art.