A microplant, starting from monomers to produce polymer particles, is described and integrates polymerization reaction, polymer analysis and nanoparticle formation in a single continuous-flow microprocess. Original contribution is brought by online polymer analysis and inline polymer nanoprecipitation. Multi-detection GPC of samples taken at the outlet of the microreactor actually enables the characterization of linear and branched polymers by combining a concentration- and a mass-sensitive detection technique. When the steady state of the microreactor is reached, micromixer-assisted nanoprecipitation of the polymer solution follows, leading to a colloidal suspension of nanoparticles with a narrow particle size distribution. Particle sizes, around 100?nm, can be tuned by process parameters.