1 . About 70% of Earth's microbes live deep in rocks that were once considered barren but where bacteria and single-celled organisms abound, according to several scientists who, for the first time, have estimated the magnitude of this "intraterrestrial" life. 2 . A pseudoscientific theory that speaks of humanoid beings living underground, either in the "hollow earth" or in underground tunnels. These beings vary depending on the theory or legend that deals with it.
