There are not many other animals as resilient as tardigrades. They can survive great depth and altitudes, tolerate temperatures from 149°C to -272°C, and even withstand a ten-day trip into low-Earth orbit and return intact despite the Sun’s ultraviolet radiation and the vacuum of space. The secret behind these superpowers is cryptobiosis: the ability to enter a reversible, death-like state when the environment gets too dry, too cold, too salty, or lacks oxygen. In this process, tardigrades expel up to 97% of their body water, stop reproduction, and stay dormand for decade until they wake up again.
Depicted above: Tardigrades (knobbly ones), Paramecium (hairy critter bottom left)
Length of Milnesium Tardigradum: ca 500 µm