Developing an understanding of the reaction processes occurring at the surface-fluid interface at the atomic level of nanostructured materials in high-temperature aqueous environments is necessary for establishing general principles of behavior of nanomaterials operating in such extremes.This understanding may also be used to more effectively model and control corrosion in supercritical-water-cooled power reactors and to achieve new insights in catalytic properties of chemically-modified metal oxide nanoparticles under extreme aqueous conditions.