Nanoclusters have gained a huge interest due to their unique properties. They represent an intermediate state between an atom and a solid, which manifests itself in their atomic configurations and electronic structure. The applications of nanoclusters require detailed understanding of their properties and strongly depend on the ability to control their synthesis process. Significant effort has been invested in modelling of nanoclusters properties. However, the complexity of these systems is such that many aspects of their growth process and properties are yet to be understood. My thesis focuses on describing structural and electronic properties of nanoclusters. In particular, the model for nanoparticles growth in plasma condition is developed and applied, allowing to describe the influence of the plasma conditions on the evaporation, growth and morphological transformation processes. The mechanism driving the morphology transition from icosahedral to decahedral phase is suggested based on force-fields models. Spectroscopic methods allow for precise characterization of nanoclusters and constitute an important tool for analysis of their electronic structure of valence band as well as core-states. The special attention in the thesis is paid to the core-states of nanoclusters and influences that affect them. In particular, the effects of local coordination, interatomic distances and confinement effects are investigated in metal nanoclusters by density functional theory methods. These effects and their contribution to spectroscopic features of nanoclusters in X-ray photoemission are modelled. The relation between the reactivity of nanoclusters and their spectroscopic features calculated in different approximations are revealed and explained. Ceria is a very important system for many applications due to the ability of cerium atoms to change their oxidation state depending on the environment. The shift of the oxidation state and its effects on the core-states is examined with X-ray absorption measurements and modelling allowing to build a rigid foundation for interpretation of the measured spectra and characterization of electronic structure of ceria nanoparticles.