The purpose of this highlight is to demonstrate the importance of the surface functionalization of nanoparticles toward the design of high-tech (nano)materials. These (nano)materials are “nano-tools” for the already established interdisciplinary research fields of nanoscience and nanotechnology, which find an enormous variety of applications in different areas. In many cases, the particle-forming material, shape, and size determine the applicability of the desired nanoparticle. Nevertheless, in most of the cases other parameters must also be accurately adjusted to transform those nano-objects into functional nanoparticles, such as dispersibility, stability, reactivity, ability to recognize (or to be recognized by) other systems, and the interaction between these parameters and a matrix or dispersing medium. Most of these parameters are mainly depending on the surface characteristics of the nanoparticles. Thus, this highlight focuses not only on the importance of the surface functionalization of the nanoparticles to render them applicable, but also on the different strategies to design and obtain surface-functionalized nanoparticles (SF-NPs) and on their successful exploitation in materials science, formulation of organic–inorganic hybrid nanostructures and bio-applications.