Polymeric Nanoparticles are predominantly prepared by wet synthetic routes. Several industrial processes will be described. Emphasis will be placed on the type of polymers and morphology structures that can be synthesized using each process. Controlled radical polymerization will be explored for their ability to provide structural control of polymer chains. The extraordinarily large surface area on the nanoparticles presents diverse opportunities to place functional groups on the surface. Particles can be created that can expand/contract with changes in pH or interact with anti-bodies in special ways to provide rapid ex-vivo medical diagnostic tests. Important extensions have been made in combining inorganic materials with polymers and in combining different classes of polymers together in nanoparticle form.