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Tardigrades, sometimes called water bears, are microscopic animals famous for surviving conditions that would kill almost anything else. They can endure being frozen, boiled, dried out for years, and even exposed to the vacuum of space. Their secret lies partly in a process called desiccation, in which they expel most of the water from their bodies and curl into a dormant ball. In this state, their metabolism nearly stops, and special protective molecules shield their cells from damage. When water returns, many tardigrades simply rehydrate and resume normal life. This ability does not make them immortal, but it gives them extraordinary resilience.