Crystals: little flakes of wonder
W.A. Bentley, Snow Crystals (New York, Dover: 1962)
Photo from Wikipedia
...perhaps not unique (no indeed, there is no chemical/scientific reason why two snow flakes should not be alike), but still marvellous. Thanks to Wilson Alwyn 'Snowflake' Bentley (1865-1931), who endured many a cold second in front of his microscope-cum-camera to capture these on film!