For people who know my photography this image is a “classic”. Still though, I thought it would be nice to share its background with you.
For several winters I enjoy visiting a small, shielded valley situated at the foot of the Eiger Mountain in the Bernese Alps, Switzerland. We use to go there in January when it is completely devoid of direct sun light. Over the years I was surprised by its particular micro-climate with often stagnant air and temperatures much lower than in the nearby village (Grindelwald). Especially when there is a stable high pressure weather regime for several days, the growth of the ice crystals can be spectacular. On one occasion that I was there, circumstances were extreme: the temperature dropped down to -30ºC for a number of days. This resulted in a fantastic cover of hoar-frost toward the end of this period. Note that the cold layer of stagnant air is only some 10 meters thick; the top branches of the tree are barely ice-covered.

Hasselblad with wide-angle and polariser, f/32, tripod, Velvia.