image

Scrolls on plate snowflake, light micrograph. Snowflakes are ice crystals that form in air that has a temperature near the freezing point of water. If the air is calm, then a symmetrical, hexagonal snowflake can form. The two main growth patterns observed are faceting and branching. When growth is fast and unstable, branching patterns create a dendritic snowflake. Slower growth allows the straight lines and hexagonal shapes of the scrolls on plate snowflake seen here, which has scroll-like growths on the apexes of the hexagon. (KEYSTONE/SCIENCE PHOTO LIBRARY/KENNETH LIBBRECHT/SCIENCE PHOTO LIBRARY)