One of nature's wonders, the hexagonal symmetry of the snowflake begins on the molecular level. Trillions of identical water molecules collect together in a cloud to form a single snowflake. Each molecule is comprised of just three atoms -- two Hydrogen and one Oxygen atom, H2O. Self-organization enables these simple ingredients to combine into intricate and endlessly variable designs. This repeating molecular structure classifies ice as a mineral. Photographs courtesy of Professor Kenneth Libbrecht at the California Institute of Technology.