Tardigrades—“water bears”—are amazing. They are mostly less than a millimetre in length, but have a complete multicellular anatomy and physiology with recognisable limbs and organs. Despite their complexity they can go dormant and become hardy little spheres of just-add-water life. In this form they are resistant to all sorts of unpleasant treatment and harsh environments. Even active tardigrades can be found everywhere from 6 000m above sea level to 4 000m below. They are extreme animals. If there’s something complicated living Out There In Space, I’d bet on it looking like a tardigrade. If you have a video player that can handle Windows Media you can marvel at a red-eyed tardigrade marching, but there are lots of still pictures and tardigrade facts here and here.