The simultaneous combination of the ring-opening metathesis polymerization of norbornene and the atom-transfer radical polymerization of methyl methacrylate is used as a convenient tool to prepare polymer composite particles in a single step and using only one catalyst. The current article reviews the use of miniemulsion and microemulsion conditions to reach this aim. The two developed approaches are assessed on chemical and colloidal levels and the prepared composite particles are scrutinized from a morphological point of view.