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This animal can dry out completely — and come back to life
💡 Tardigrades survive extremes not by resisting damage but by expelling their water and turning to glass, pausing life until water returns.
The tardigrade — a water-dwelling animal under a millimeter long, nicknamed the "water bear" — can survive things that would instantly kill almost anything else: boiling heat, the vacuum of space, radiation hundreds of times the human lethal dose, and pressures deeper than any ocean trench. Its secret isn't toughness in the usual sense. It's the ability to stop being alive for a while.
When its environment dries out, a tardigrade pulls in its legs, expels almost all its body water, and curls into a shriveled ball called a tun. In this state its metabolism falls to undetectable levels — arguably zero. This suspended condition is called cryptobiosis ("hidden life"). A tun can sit inert for years, then swell back to a walking, eating animal within minutes of a drop of water.
How does drying out not shred the cells? As water leaves, tardigrades flood their tissues with special disordered proteins (called CAHS proteins) that harden into a glass-like solid, encasing and cushioning delicate molecules in place. With no liquid water, the chemistry of decay simply can't run — so the animal isn't damaged; it's paused. This is why cryptobiosis is more like vitrifying into glass than like slowing down a running engine.