We have studied the electromagnetic response of different geometries of High Refractive Index Dielectric (HRID) nanoparticles, in order to analyze possible applications of this kind of nanostructures. In particular, isolated particles or aggregates have been considered. For the former, the great capabilities of either pure or metallo-HRID core-shell nanoparticles for sensing purposes have been evidenced. High sensitivity values to changes in the refractive index of the surrounding medium and to the degree of purity of the material, which they are made of, have been obtained. In addition, the electromagnetic behavior of those structures as a function of the nanoparticle size has been investigated, demonstrating their sizing applications. Moreover, it has been evidenced that by changing the core size respect to the particle size, the Scattering Directionality Conditions (SDCs) can be enhanced or disabled. In order to go deeper into the possibility of using these nanostructures for enhancing the SDCs, eccentric metallo-dielectric core-shell nanoparticles have been explored. Depending on the core displacement from the nanoparticle center, different applications have been shown. For core shifts perpendicular to the propagation direction of the incident radiation, the possibility of utilizing these units for building switching devices has been exposed. For core displacements parallel to the propagation direction of the incoming wave, both SDCs can be enhanced. Enhancing the Zero-Backward condition is important for applications, which require redirection of the incident radiation in forward, like solar cells. Following this idea, the Zero-Backward condition has been studied for different particle shapes. Some of the analyzed applications can be improved by means of aggregates of HRID subwavelength particles. Through dimers, it has been exhibited that it is possible to observe more efficient switching effects than that obtained with eccentric core-shell nanoparticles. The dimer confguration can also be useful for improving the performance of photovoltaic devices. By using silicon dimers, two spectral regions where the incident intensity is mainly scattered in the forward direction can be found. With the objective of going further in the possibility of using HRID nanoparticles for solar cells applications, the fraction of radiation that is scattered into the photosensitive substrate has been analyzed when aggregates of HRID nanoparticles are located on its surface.