Bdelloid rotifers are multicellular animals so small you need a microscope to see them. Despite their small size, they're known for being tough, capable of surviving through drying, freezing, starvation, and low oxygen. Now, researchers reporting in the June 7, 2021 issue of Current Biology, have found that not only can they withstand being frozen, but they can also persist for at least 24,000 years in the Siberian permafrost and survive. The article is titled “"A Living Bdelloid Rotifer Recovered from 20,000 Year Old Arctic Permafrost." "Our report is the hardest proof, as of today, that multicellular animals could withstand tens of thousands of years in cryptobiosis, the state of almost completely arrested metabolism," says Stas Malavin, PhD, of the Soil Cryology Laboratory at the Institute of Physicochemical and Biological Problems in Soil Science in Pushchino, Russia.