I was actually hiking ON the frozen surface of a creek (Antelope Creek) near our home in Colorado. The creek had still been partially open at a few spot just two days earlier, but after a few days of extreme cold temps the creek was now solidly frozen. At one point I was looking down at the ice and saw these super tiny air bubbles that were literally frozen in mid-motion when the flowing water turned rapidly to ice during the hard frost. I decided to lie down on the frozen creek to take a few macro shots. And I was stunned: It felt like as if I was getting a glimpse at another world. A cosmos in a creek. Sparkling, downright alien. Also, I had always assumed air bubbles would have a smooth outside wall but instead - as one can clearly see - the "skin" is rough like rocks. The entire area depicted in this image was only half an inch across.