A final difficulty in starting the life-process is the formation of the first living cell. Mike Russell of the University of Glasgow has proposed that such a process may have had a non-living counterpart in the sulphide bubbles which form at hydrothermal vents. He has suggested that iron sulphide (FeS) can in some circumstances form a chemical membrane. This non-living chemical membrane forms a base from which organic molecules can 'learn' to form an organic membrane and thereby form a sac in which the vital molecules of DNA can be safely stored. For details see http://www.gla.ac.uk/projects/originoflife/html/2001/index.htm (go to 'show origin of life model', bottom right of figure; for greater detail go to the section on 'Organic Membrane').