(WUTR/WFXV/WPNY) – Snowflakes can come in so many intricate shapes and patterns but still look the same to the naked eye. Upon closer look under a microscope, you can see the beautiful designs that mother nature creates. How do they form? In short, snowflakes form when water vapor travels through the air and condenses on a particle. This begins to form a slowly growing ice crystal (a snowflake!). There are two basic ways that the vapor can condense, and each-way plays a big role in the shape that the snowflake will eventually take.

Microscopic view of snowflakes by Wilson Bentley. From the Annual Summary of the Monthly Weather Review for 1902. Bentley was a farmer whose hobby was photographing snowflakes. Source: NOAA Photo Library archives Weather Wonders collection, www.photolib.noaa.gov. (NOAA)

The first way is to form what are called ‘facets.’ A facet is essentially a flat face on a 3D shape, like a prism. They form naturally when a crystal grows. In ice crystals, the shape they take mirrors the shape of the molecules forming the crystal. The crystal structure of frozen ice is a six-sided shape. Therefore an icy facet is six-sided as well. That is where the symmetry in a snowflake comes from.

The second way to grow a snowflake is to form branches. Not surprisingly, this is what creates those beautiful tree-like structures. Branches form because water vapor will condense on the first thing it touches. If there is a small bump on a snowflake’s surface, the vapor will condense there instead of traveling any further. Now the bump is bigger and even more likely to ‘catch’ water vapor at that point. The process repeats itself and a branch is formed!

Why do no two snowflakes look alike? The intricate shape of a single arm of the snowflake is determined by the atmospheric conditions experienced by the entire ice crystal as it falls. Since individual snowflakes all follow slightly different paths from the sky to the ground, they encounter slightly different atmospheric conditions along the way. Therefore, they all tend to look unique, resembling everything from prisms and needles to the familiar lacy pattern.