Archaebacteria are the most recent addition to the kingdoms of organisms. Their existence was not discovered until the 1980s. However, Archaebacteria are the oldest known living organisms. They are single-celled and thrive in extremely hot boiling water found in environments like volcanic thermal vents in the ocean and hot springs like the geysers at Yellowstone Park. Some species also live in very salty environments such as The Dead Sea and The Great Salt Lake.