It is generally agreed that process intensification requires a holistic view of the process, considering the process as a whole system. However, there is no general consensus about the extent of improvements necessary in order to earn the label “process intensification”. In our view, these should be drastic improvements of at least an order of magnitude. These improvements may include e.g. a reduction of the plant size by reducing the size of single apparatuses or by reducing the number of the latter by integrating two or more unit operations into a multifunctional unit. Other intensification potentials concern e.g. the specific energy consumption, the amount of reactants used and of waste products being produced for a specified production height (i.e. the feedstock efficiency). A successful intensification of a chemical process requires a systematic debottlenecking which is obtained by identifying and eliminating the main transport resistances that limit the overall process performance and thus can be considered as rate-determining steps on the process level. In our work, we will present an approach that is not based on classical unit operations, but on the analysis of the basic functional principles that are encountered in all processes. Each chemical process can be broken down into five types of elementary function units. Again, it is important to note that we are discussing the elementary function itself (i.e. the underlying physics), and not the function already as part of a unit operation. In the center of the chemical process we define the first elementary function as the “reaction function”. The chemical reaction function must be supplied with reactants. In addition, an adequate contacting of the reactants has to be ensured (“contacting function”) and the reaction needs to be activated (“activation function”). As a result of the reaction function we generally obtain a mixture of different products (and the fraction of the reactants that have not been converted), so that the introduction of a “separation function” is necessary. Since an energy exchange with the environment takes place during the reaction we finally need an “energy transport function”. In our contribution, we will first present the concept of elementary process functions by discussing individually the different functions and the pool of possibilities we have for process intensification measures at each stage. Then we will analyze selected examples of successfully intensified chemical processes and identify and classify the measures according to our elementary function scheme. However, the idea here is not only to optimize an existing process but rather to derive generalized guidelines for the decisions to take for the different elementary process functions in the conceptual design of an intensive chemical process.