The Archaea are single-celled prokaryotic organisms in a distinct domain from bacteria and eukaryotes. In the past, the archaea were classified together with the bacteria in Kingdom Monera (and were called archaebacteria), but more recent analysis of biochemical and genetic information have resulted in their separate classification. Archaea were first identified in extreme environments, such as hot springs, but since then they have been found in a variety of habitats, including the soil and the ocean.