The miniemulsions process represents a versatile tool for the formation of polymeric nanoparticles consisting of different kinds of polymer as obtained by a variety of polymerization types ranging from radical, anionic, cationic, enzymatic polymerization to polyaddition, and polycondensation. The process perfectly allows the encapsulation of hydrophilic and hydrophobic liquids and solids in polymeric shells, molecularly dissolved dyes or other components. In combination with a specific functionalization of the nanoparticles' or nanocapsules' surfaces and the possibility to release substances in a defined way from the interior, complex nanoparticles or nanocapsules are obtained, which are ideally suited for application in biomedical application as marker and targeted drug-delivery system. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 493-515, 2010