Polymeric micro- and nanoparticles receive the attention of researchers in different areas such as drug delivery, sensing, imaging, cosmetics, diagnostics, and biotechnology. However, processes with conventional equipment do not always allow precise control of their morphology, size, size distribution, and composition. On the other hand, microreaction technology offers improved control over the hydrodynamics, mass and heat transfer, allowing production of polymeric particles with better defined or new characteristics. Thus new horizons in polymer particle engineering arise from the use of microstructured or microfluidic devices. This article gives an insight into the latest developments and trends in the production of polymeric micro- and nanoparticles realized by microreaction technology directly.