Solid state composites, being constructed of inorganic/inorganic building blocks, combine the ability of the parent constituents and generate new, sometimes unexpected, properties. The enrichment of the composites in silicon can be proven with optical methods. This chapter considers the optical, structural and light-emitting properties of the composite materials, based on the different dielectrics with embedded Silicon (Si)-nanoclusters (NCs) or germanium (Ge)-NCs fabricated by magnetron sputtering. In supersaturated Si-rich composites with a higher Si excess, an appearance of Si nuclei occurs via spinodal decomposition and governed by oxygen out-diffusion from some spaces towards interface shells between Si seeds and SiO2 hosts. Among the different approaches used for Si- and Ge-NCs' production, magnetron sputtering is one of the flexible methods allowing the growing of composite films and superlattices. To investigate the formation of Si-NC in the HfO₂ host, composite thin films were grown on Si and fused quarts substrates by magnetron sputtering of the composed target.