Fabrication of inorganic nanoparticles is now a mature field. However, further advances, in particular in the field of catalysis, require a more accurate description of their surface and of the transformations occurring beneath the surface in the environment of use. Through a selection of case studies, this feature article proposes a journey from surface science to nanoparticle design, while illustrating state-of-the-art spectroscopies that help provide a relevant description of inorganic nanoparticles in the context of surface reactivity.