William Wergin did not set out to be the king of snow. He always thought of himself as more of a botanist and a nematode guy, studying how parasitic soil-dwelling worms interact with crop plants. Then in December 1993, he and Eric Erbe, a colleague at the U.S. Department of Agriculture’s Electron Microscopy Unit in Beltsville, Maryland, started experimenting with a newly configured low-temperature scanning electron microscope.
The custom-built device keeps samples chilled to –320 degrees Fahrenheit, making it possible to flash-freeze nematodes or insects and then magnify them enormously to observe their behavior at a single moment in time. Wergin and Erbe couldn’t get their hands on a suitable agricultural sample, so they decided to try their new toy on some of the snowflakes falling outside.
“We had nothing else to image,” Wergin says. The two researchers collected flakes on a copper plate and brought the crystals indoors to their microscope. Fellow USDA researcher Al Rango, now at the department’s Jornada Experimental Range in Las Cruces, New Mexico, stopped by the lab and was stunned by the results. “I’d seen a lot of snow-crystal imagery, but I had never seen crystals this way before,” he says.
