A process for preparing nanoscale azo pigment particles includes providing an organic pigment precursor that contains at least one functional moiety, providing a sterically bulky stabilizer compound that contains at least one functional group, and carrying out a chemical reaction to form a pigment composition in a microreactor or micromixer, whereby the functional moiety found on the pigment precursor is incorporated within the pigment and non-covalently associated with the functional group of the stabilizer, so as to allow the formation of nanoscale-sized pigment particles and the production of such in a microreactor under laminar or turbulent flow conditions without clogging.