Canadian-born photographer and performance artist Michael Grab began exploring the ancient discipline of rock balancing in the summer of 2008 while hiking around Boulder Creek in Boulder, Colorado. It has since become a daily meditative practice for him, and it's not uncommon for him to draw small crowds of spectators as he creates these meticulous, ephemeral installations. "I am constantly in awe at the stillness, let alone possibility, of such precarious formations, amidst sometimes very turbulent conditions," Grab explains on his website, Gravity Glue. "For me, this reflects our own potential to maintain a still-point amidst the variety of challenges we each face throughout our lives." So how does he do it? Many of his seemingly gravity-defying sculptures look so out of this world that you might think adhesives, wires or other external supports were used, but Grab says that the only thing that holds these objects in equilibrium is gravity.