The Domain Archaea is separated from the other two domains by several distinguishing characteristics. The organisms that are in Domain Archaea are prokaryotic, have ether-linked and branched membrane lipids, and live in extreme environments of which  most organisms cannot live in, for example: saline environments with 5.0 M NaCl; or anaerobic environments. Domain Archaea is also discernible from Domain Bacteria by its cell wall structure and ribosomal structure. Domain Archaea has two major Kingdoms: Euryarchaeota and Crenarchaea (Holt, 2011). There also exist two minor kingdoms: Korarchaeota and Nanoarchaeota.