To categorize surfaces as hydrophobic or hydrophilic by measuring contact-angles is a step toward understanding water-solid interactions, but a small one. To predict wetting, control aqueous surface chemistry or design nanofluidic systems, atomic-scale understanding of water-adlayer structure and dynamics is wanted. The research involved is risky -- systematic error is an ever-present concern in dealing with weakly interacting species, like water, which are commonplace in the natural world. To explore the limits of current ab initio methods for water on solids, I have been applying first principles Density Functional Calculations to the simplest examples: periodic water adlayers on close-packed, precious metal surfaces. On Ru(0001), the calculations invite the inference that wetting involves forming a half-dissociated monolayer with water molecules and hydroxyl fragments hydrogen-bonded in a hexagonal structure and hydrogen atoms bound directly to the metal. Refinements of this idea are needed, however, to make contact with measured vibration spectra. New understanding is also necessary to explain the occurrence of periodic adlayers on surfaces like Rh(111) and Pt(111), too unreactive to make dissociation energetically favorable, and to give meaning to beautiful STM images of water clusters obtained at LBNL on Pd(111). @FootnoteText@ @footnote 1@Work supported in part by the DOE Office of Basic Energy Sciences, Division of Material Sciences and Engineering. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE- AC04-94AL85000.