Little more than 30 years since the discovery of the Archaea, over one hundred archaeal genome sequences are now publicly available, of which ∼40% have been released in the last two years. Their analysis provides an increasingly complex picture of archaeal phylogeny and evolution with the proposal of new major phyla, such as the Thaumarchaeota, and important information on the evolution of key central cellular features such as cell division. Insights have been gained into the events and processes in archaeal evolution, with a number of additional and unexpected links to the Eukaryotes revealed. Taken together, these results predict that many more surprises will be found as new archaeal genomes are sequenced. Copyright © 2011 Elsevier Ltd. All rights reserved.