Mixing of concentrated suspensions of rigid particles or nanoparticles incorporated into a liquid binder (especially via continuous processing) is a major processing challenge. This challenge stems to some extent from the development of the viscoplasticity and the wall slip behavior of concentrated suspensions on one hand and the possible “demixing” and segregation of the ingredients of the suspension into distinct phases during processing on the other. Processing of concentrated suspensions always involves a superposition of the dynamics of the mixing and demixing phenomena, with the resulting microstructures affected by the details of the thermo-mechanical history that the suspension is exposed to. Here, examples of concomitant occurrences of various mixing and demixing processes will be provided in conjunction with cellulose based aqueous suspensions and carbon nanotube based polymeric nanosuspensions. Various ways of the characterization of goodness of mixedness measures, “mixing indices”, and methods of generating suspensions that are more robust to demixing effects will be presented.