The fourth volume of Water Science Reviews presents three fascinating accounts of hydration phenomena in collodial systems. O. Fennell Evans and David Miller provide a reappraisal of the role of water in promoting amphiphilic assembly and structure. Donald Eagland's review of water-soluble polymers highlights those which show unique solution properties or where there is contention as to the explanation for the behaviour. The final review, from Kenneth Newman, deals with the hydration of surfaces, a topic of profound scientific and technological importance.