They are in fact... snowflakes. From Tech News Daily:
Researchers at the University of Utah have developed the Multi Angle Snowflake Camera (MASC), which uses three high-speed cameras triggered by infrared sensors to shoot flakes as they float to the ground, with exposures as quick as 1/25000 of a second. The device also measures the flakes' fall speed, all without touching them, which would disturb the measurements.
And while the images are pretty, their accuracy could be useful, too allowing meteorologists to create more accurate model of winter storms. [Tech News Daily]
Image by University of Utah