Process intensification follows four main goals: to maximize the effectiveness of intra-and intermolecular events, to give each molecule the same processing experience, to optimize the driving forces/maximize specific interfacial areas, and to maximize the synergistic effects of partial processes. These goals can be achieved in four domains: spatial, thermodynamic, temporal and functional. The paper shows how these goals can be reached in fluid separation processes. In doing so, each of the four domains are examined separately moving across all relevant time and length scales, from the molecules to the processing unit plant.