Crenarchaeol is a large, closed-loop lipid that is present in the membranes of ammonium-oxidizing archaea. In comparison to other archaeal membrane lipids, crenarchaeol is very complex and, so far, attempts to confirm its structure by synthesizing the entire molecule have been unsuccessful. Organic chemists have now taken up this challenge and discovered that the proposed structure for the molecule was largely, but not entirely, correct.