Tardigrades — microscopic eight-legged animals — have survived boiling water, radiation, the vacuum of outer space, and pressures six times deeper than the deepest ocean.

Tardigrades, nicknamed "water bears," are 0.5 mm long and live almost everywhere on Earth — in moss, soil, leaf litter, and ocean sediment. They look like tiny chubby caterpillars with eight stubby legs. Under a microscope they are almost cute. Under stress, they are nearly indestructible.

When conditions become hostile, tardigrades enter a state called cryptobiosis — they retract their legs, expel almost all water from their bodies, and effectively shut down all metabolism. In this desiccated state, called a "tun," they can survive temperatures from −272°C to +150°C, pressures of 6,000 atmospheres, intense radiation doses 1,000 times lethal to humans, and the complete vacuum of space. They were sent on a satellite and survived.

The key to their survival is a special protein called Dsup (Damage Suppressor) that physically wraps around their DNA like a shield. Scientists have successfully transferred the Dsup gene into human cells in a laboratory — those cells became significantly more radiation-resistant. Tardigrades may eventually help us protect astronauts on long space missions.

Find some moss on a wall, rock, or pavement and scrape a tiny piece into a jar of water. Leave it for an hour, then look at a drop under a magnifying glass or phone macro lens. You have a real chance of seeing actual tardigrades — they live in moss all over the world.