This invention discloses a process for making nanoparticles of amphiphilic copolymers by flash precipitation. Nanoparticles may be of amphiphilic copolymer alone or may contain an additive target molecule, preferably an organic active. The inclusion of additive target molecules in amphiphilic copolymer nanoparticles can alter their water solubility characteristics, fluid dynamics, and/or stability. Changing an additive target molecules solubility and stability in a nanoparticle can make a water insoluble compound suitable for pharmaceutical administration as well as specifically target the molecule to a specific area of a patients body. The process affords the production of nanoparticles at high absolute active content, at high yield, high productivity, and high processing rates while using unusually low amounts of amphiphilic copolymers. Furthermore, the resulting particles exhibit sufficient stability for post processing as desired. The invention also discloses two apparatuses for the production of nanoparticles of amphiphilic copolymers by flash precipitation.