We present a novel method for systematic process design and intensification. We depart from the classical unit operation-based representation of process units, flowsheets and superstructures and propose a new representation using fundamental building blocks. These building blocks can be associated with different process phenomena, tasks and unit operations. An assembly of blocks of the same type obtains a classical unit, while an assembly of blocks with different types results in an intensified unit. This allows to systematically identify and incorporate many intensification pathways using a general block-based superstructure. We design an intensified process by optimizing a performance metric for given raw materials and product specifications, material properties and bounds on flow rates. The overall problem is formulated using a single mixed-integer nonlinear optimization (MINLP) model that can be solved using commercial solvers. We show the applicability of our approach using several design and intensification case studies. (C) 2017 Elsevier Ltd. All rights reserved.