The Kingdom Monera encompass all prokaryotic, unicellular, organisms. This has been further divided into many groups, Cyanobacteria, Eubacteria, Archaebacteria, etc. 

The Archaebacteria are differentiated from other bacteria on the basis of their different cellular features. They show the presence of branched chain lipids in cell membrane than eubacteria. That increases tolerance against adverse conditions. They are called extremophiles.