![Snowflakes: Perfectly shaped snowflake on a green leaf. It has 6 fern-like arms.](jpg/snowflake-sheryl-garrison-november-9-2022.jpg)
Exquisite crystalline snowflakes capture the imagination. But what is the science behind their formation, and is it true there are no two snowflakes alike?
First of all, the temperature and humidity of the atmosphere determine the shapes of snowflakes. And snowflakes form in the atmosphere when cold water droplets freeze onto dust particles. Finally, depending on the temperature and humidity of the air where the snowflakes form, the resulting ice crystals will grow into a myriad of different shapes.
![Graph: temperature on X axis, humidity on Y axis, with different kinds of snowflakes.](png/snowflakes9of9-shapes-temperature-vs-saturation-noaa.png)
Wilson Bentley
Wilson Bentley (1865–1931) from Jericho, Vermont, was the first person to capture photographs of snowflakes through a microscope attached to a camera. His collection of over 5,000 images – no two alike – introduced many people to the astounding diversity of snow crystals.
![A man in a winter coat and a hat standing in front of a large, old-fashioned camera setup on a table outside.](jpg/wilson-bentley-portrait-with-camera-photographing-snowflakes-wikimedia-1931.jpg)
![Nine snowflakes in shapes ranging from a flat hexagon to complex 6-branched flakes.](jpg/9-snowflakes-wilson-bentley-collection-wikimedia.jpg)
Classification systems
In 1951, scientists from an organization now called the International Association of Cryospheric Sciences (IACS) devised a classification system that characterized snowflakes into 10 basic shapes. Kenneth Libbrecht, professor of physics at the California Institute of Technology, in his guide to snowflakes at SnowCrystals.com, provides this chart of 35 types of snow crystals. They range from ice fragments to rods to the much more complex fern-like dendritic flakes we are all familiar with.
![Chart with 35 drawings of different shapes from flat to rods to six-sided fernlike flakes.](jpg/snowtypes4-chart-kenneth-libbrecht-e1706028716108.jpg)
How snowflakes form from water vapor
Libbrecht has made extensive observations of how water molecules get incorporated into snow crystals. In his research, he observed that the most intricate snowflake patterns form when there is moisture in the air. Snowflakes produced in drier conditions tend to have simpler shapes.
According to Libbrecht’s research, temperature also has a large effect on the formation of snowflakes. Snowflakes formed in temperatures below -7.6 degrees Fahrenheit (-22 degrees C) consist primarily of simple crystal plates and columns. Meanwhile, snowflakes with extensive branching patterns are formed in warmer temperatures.
Visit Libbrecht’s website SnowCrystals.com for a wealth of information about snowflakes, including short videos of lab-grown snowflakes forming.
![Closeup of feathery, translucent six-armed snowflakes.](jpg/snowflakes-fiona-m-donnelly-e1515593080596.jpg)
A gallery of snowflakes by Wilson Bentley
![A snowflake with six delicately branched points.](jpg/spiky-wilson-bentley_snowflake_785-wikimedia-e1705933533994.jpg)
![Flat white hexagon with dark lines from center to corners.](jpg/hexagonal-wilson-bentley_snowflake_869-wikimedia-e1705933556623.jpg)
![Snowflake with six delicate, complex branches.](jpg/delicate-wilson-bentley_snowflake_815-wikimedia-e1705933574129.jpg)
![Snowflake with six delicate, bulbous crystal branches.](jpg/bentley_snowflake11-fins-small-wikipedia.jpg)
Bottom line: Temperature and humidity influence snowflake shape. The most intricate snowflake patterns form during warm and wet conditions.