Preparing filled rubber compounds is achieved through quite a complex sequence of operations that under the general heading "mixing" hide a more or less complicated series of physico-rheological events. On the factory floor, actual mixing operations essentially result from pragmatic experience, sometimes without much clear understanding. Starting from simple considerations about the basic objectives of mixing, with respect to most recent findings about rubber - filler morphology, the paper will focus on fundamental aspects of this important processing step, Investigations about the kinetic aspect of carbon black dispersion in rubber and the links that can be demonstrated between bound rubber and flow properties, show that those are important criteria in understanding the complexity of rubber mixing.