The acidity abd reactivity of surface on amorphous and crystalline polymorphs of silica and other oxides control their thermodynamic stability and kinetic reactivity towards reactants in surface-controlled processes of environmental, industrial, biomedical and technological relevance. Recent advances in computational methodologies such as CPMD and increasing computer power combined with spectroscopic measurements are now making it possible to link, with an impressive degree of accuracy, the molecular-level description of these processes to phenomenological, surface complexion models The future challenge now lies in linking mesoscale properties at the nanometer scale phenomenological models that will afford a more intuitive understanding of the systems under consideration.