(Bio)polymer synthesis, modification and multilayer/shape production for e.g. (food) packaging, recycling, food production, and pharmaceutical/composite applications are characterized by a highly viscous reaction environment, complicating large scale production with reproducible product homogeneity and high yield. An interesting technique to facilitate highly viscous processing is extrusion (EX) in which grains are converted via a screw configuration in a material shape. Important advantages are excellent mixing and heat transfer, and continuous production. If chemicals are added a reactive extrusion (REX) results with the advantage of combining compounding and synthesis in one equipment so that a final (multi)material can be directly obtained. An EX challenge is process control from the molecular to the material scale for a wide range of (bio)polymer blends. For REX, this challenge also exist with the additional desire to apply this technology for a broader range of chemistries. A challenge also lies in process design along the whole processing unit. To solve these challenges a fundamental multi-scale understanding of (R)EX is needed from lab to pilot and finally industrial scale. Essential is validation of multi-scale parameters based on universal multifunctional (R)EX equipment, as requested. The application is supported by 5 UGent Faculties and joint projects with other universities are already defined (13 letters of intent).