Billede:Snowflake 300um LTSEM.jpg

Low temperature scanning electron microscope [1] magnification series, from 93x to 36,000x magnification series, of a snow crystal.

Most samples of snow crystals are observed by researchers at relatively moderate magnifications (30X-500X), however the capabilities of the electron microscope allow observation of fine structures at over 100,000X. The following set of photographs demonstrates a magnification series using a low temperature scanning electron microscope (LT-SEM) covering this range. By contrast, the light microscope is only capable of viewing meaningful details at magnifications of about 1,000X and is very limited in depth of field. Snow samples are very fragile and exposure to the light necessary to photograph them, using light microscopes, can change structures and even melt them. Using LT-SEM, samples are frozen to temperatures below -170 degrees Centigrade where they can be placed in a vacuum and observed for many hours with no structural changes. These photographs show the extraordinary symmetry of snow crystals even at high magnification. Magnification bars are accurate but X factors (lower left) are for 8"x10" prints.

   Downsampled version is here: Image:Snowflake 300um LTSEM_Edited.jpg

Source: http://www.anri.barc.usda.gov/

This image is in the public domain because it contains materials that originally came from the Agricultural Research Service, the research agency of the United States Department of Agriculture.