Colloidal syntheses of various metal and semiconductor nanoparticles are established as a powerful tool to control their composition, size, size distribution and physico-chemical properties. The assembly of colloidal nanoparticles can be performed on flat, porous and spherical surfaces, thus being important for thin-film technologies, doping of mesoporous materials, modification of pre-patterned substrates, creation of microshells and cavities, supported catalysts, etc. Self-assembly approaches or the use of removable templates make possible the formation of nanowires or nanoporous 3D ordered materials created solely from the assembled nanoparticles. Hierarchical assembling and assembling of nanocrystals with other organic or inorganic entities open up a possibility to achieve composites with literally unlimited functionalities. The understanding and governing of the assembly processes are the key points in their efficient utilization for novel types of applications, including optoelectronic, photovoltaic and photonic devices, optical sensors, heterogeneous- and electrocatalysts.