Frozen greenhouse beauty

Every once and a while the windows of my unheated greenhouse freeze with beautiful designs. The weather has to be just right for this to happen. The windows thaw a bit during the day then when they freeze ice forms in these intricate patterns. Believe it or not, these are color pictures, but the way the light hits the glass they take on the appearance of black and white etchings, at least that's what they look like to me. Nature is amazing, isn't it?