Nanoparticle assemblies are emerging highly promising materials, which aim at making use of nanoparticles collective properties. The synthesis pathway to create nanoparticle assemblies ensures the control on the distance between the nanoparticles. Various pathways will be presented for the formation of nanoparticle assemblies: such as template-assisted or pressure-induced synthesis, layer-by-layer or evaporation-induced deposition, introduction of a molecular linker. Nanoparticle assemblies can address many cutting-edge applications like plasmonic, sensoric, or catalysis.