There are many different types of snowflakes; the temperature determines which type of crystal will form. Snowflakes that form at just below freezing are are small, six-sided plates. When it is a few degrees cooler, snowflakes generally form as six-sided, pencil-like columns. At about 5° Fahrenheit (minus 15° Celsius), snowflakes mostly take the form of large, fern-like plates. Other shapes include slender needles, hollow columns, columns with caps, double plates, and truncated triangles (triangles with the ends chopped off).

People have been interested in snowflakes for a long time. In 1611 (long before the invention of the microscope), the German astronomer Johannes Kepler (1571-1630) was the first person to write about the 6-sided symmetry of snowflakes. In 1635 (still before the invention of the microscope), the French scientist René Descartes (1596 -1650) carefully noted the structure of snowflakes, including some rare forms of these ice crystals. In 1665, Robert Hooke, an English scientist, used the newly-invented microscope to describe many things, including snowflakes.

The first person to photograph snowflakes was Wilson A. "Snowflake" Bentley (1865-1931), from Jericho, Vermont, USA. Bentley was homeschooled by his mother, who had been a school teacher. At 15 years old, he began investigating snowflakes. Bentley developed his own instruments, a bellows camera attached to a compound microscope that could photograph the tiny, delicate crystals before they melted. The first snowflake photo was taken by Bentley in 1885. Altogether, Bentley photographed over 5,000 snowflakes; he published his snowflake images in journals and in a book.

Ukichiro Nakaya (1900-1962), a Japanese nuclear physicist, studied snow crystals, classifying them in the 1950s and investigating how they formed.