Sextillions of snowflakes fell from the sky this winter. That's billions of trillions of them, now mostly melted.

Kenneth Libbrecht, a professor of physics at the California Institute of Technology, has spent a quarter-century trying to understand how such a simple substance — water — could freeze into a multitude of shapes. "How do snowflakes form?" Libbrecht said during an online talk hosted by the Bruce Museum in Greenwich, Conn.

One of the people intrigued by Libbrecht's snowflake research and photography was Nathan Myhrvold, a former chief technology officer at Microsoft and an avid photographer. In spring 2018, he decided he wanted to take pictures of the intricate frozen crystals. "It turned out to be massively more complicated than I thought," he said. "I came up with a custom optical path."

Myhrvold also found a special LED, manufactured by a company in Japan for industrial uses, that would emit bursts of light 1/1,000th as long as a typical camera flash. This minimizes heat emitted from the flash.

To look at something under a microscope, a specimen is typically placed on a glass slide. But glass retains heat. That also melts the snowflakes. So he switched from glass to sapphire, a material that cools more readily.

When temperatures are just below freezing, the snowflakes are generally simple hexagon plates. At about 20 degrees, the prevalent shape is hexagonal columns. It is between 15 degrees and 5 below Fahrenheit that the archetypically beautiful snowflakes usually form.

At these temperatures, the points of the hexagon grow into branches, which spawn other branches and smaller hexagonal plates. Variations in the temperature and humidity affect the growing pattern, and the conditions are constantly changing as the snowflake falls.

"Because it has this complicated path through the clouds, it gives a complicated shape," Libbrecht said. "They're all following different paths, and so each one looks a little different."

Thus, to find the beautiful snowflakes, Myhrvold and a couple of assistants lugged about 1,000 pounds of equipment to Fairbanks, Alaska; Yellowknife in the Canadian Northwest Territories; and Timmins, Ontario, about 150 miles north of Lake Huron. Myhrvold took what he calls the highest resolution images of snowflakes ever.

That claim has irked others, including Don Komarechka, a Canadian photographer who uses a store-bought digital camera with a high-power macro lens. He does not even use a tripod — he just holds the camera while the snowflakes sit on a black mitten that his grandmother had given him.

"Incredibly simplistic," he said.

Komarechka also takes a different approach to illumination, using light reflected off a snowflake, while Myhrvold's images capture light passing through. "You get to see surface texture and sometimes beautiful rainbow colors in the center of a snowflake," he said.

To counter Myhrvold's claims, Komarechka took an image that he said was even higher resolution.

In practical terms, Myhrvold's images are sharper when printed on paper at expansive sizes.

"In that very narrow sense, yep, that's what Nathan is claiming, and he's not wrong," Komarechka said.