These tiny water bears, called Tardigrades (meaning "slow stepper"), are water-dwelling, eight-legged, segmented micro-animals. They have been sighted from mountaintops to the deep sea, from tropical rain forests to the Antarctic.

Tardigrades are notable for being perhaps the most durable of known organisms; they are able to survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from 1 K (−458 °F; −272 °C) to about 420 K (300 °F; 150 °C), pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. They can go without foo ...