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