Fifty years ago biologists hypothesized that snakes slither by pushing their bodies against branches and debris. But how do snakes slither on smooth surfaces? Mechanical engineer David Hu, of Georgia Tech, and his colleagues filmed snakes slithering up inclines and sliding down plains. They outfitted the snakes in socks and photographed them through jello, all to better understand snake locomotion. The researchers published their findings in the Proceedings of the National Academy of Sciences.