Hellish Hot
Credit: A. G. Borgonie, Ghent University, Belgium

With a length of just 0.02 inches (0.5 millimeters), these tiny nematodes called Devil's worm are the deepest terrestrial multicellular organisms on Earth. The worms were discovered at a depth of nearly a mile (1.3 kilometers) in a South African gold mine; the species was named Halicephalobus mephisto for the Faust legend of the devil, as the new species must survive immense underground pressure and devilish-hot temperatures. (Worm is shown here in a scanning electron microscope image.)