When provoked, the itsy-bitsy invertebrates known as tardigrades can suspend their metabolism. In that state, they can survive temperatures of... 73 K for days on end, making them hardy enough to endure being stranded on Neptune. So the next time you need space travelers with the right stuff, you might want to choose yeast and tardigrades, and leave your astronauts, cosmonauts, and taikonauts at home.