In order to completely master a polymerisation process, it is necessary to take a pluri-disciplinary approach that incorporates the use of kinetic and polymer property models (e.g. of R-p, the rate of polymerisation and of copolymer composition distribution, CCD), hardware and software sensors, non-linear observers for the data interpretation, and easily tuneable, robust controllers for the optimal and safe operation of reactors that produce polymer of a pre-specified quality. An overview of the results obtained in this area show that such an approach allows not only to follow and control production rates and the evolution of the CCD, but to obtain other useful process information on the evolution of such properties as the number of particles per litre of emulsion (N-p) and the number of radicals per particle (ii) in emulsion polymerisation, dr the overall termination rate constant in solution reactions. It is also shown that this method can be used not only for reactor control, but also for fault detection and process optimisation.