The production of drug nanoparticles is a promising method to enhance dissolution behavior and, by that, bioavailability of poorly soluble drugs. In this study, fenofibrate nanoparticles were produced via high-pressure antisolvent precipitation (HPAP) using a customized microsystem. The benefit of microfluidic systems is the defined streaming behavior inside the microchannels resulting in homogeneous products produced via a continuous process. Formulation strategies (e.g. fenofibrate mass fraction) as well as process parameters (e.g. pressure) were studied to evaluate their influence on particle size and size distribution. Furthermore, the streaming and mixing behavior in the microchannels were visualized via micro particle image velocimetry (mu PIV) and laser induced fluorescence (LIF) in order to elucidate the mechanisms inside the microchannels as well as to support the results obtained from HPAP experiments.