How can an ascent to the top of Everest help to save lives in intensive care? This week we're exploring physiology at the extremes: altitude, depth and cold. How does the human body adapt and cope under these conditions? Also, news of improved gene therapy techniques for sight-loss disorders, when do babies become sympathetic, how to cloak your cat (or goldfish), and have scientists discovered the remains of the Tunguska meteorite that smashed into Siberia in 1908?