The aim of this project ASSEMBLE is to manufacture high temperature heat exchangers (HEX) and associated reactors operating above 800°C using the powder metal 3-D printing process of selective laser melting (SLM). Optimization and integrity verification of the printed parts will be carried out by CFD modelling, materials and component analysis and by x-ray computed tomography (CT). The combination of this novel manufacturing method together with a specific characterization method will make it possible to obtain more efficient, lighter, more compact and more reliable high temperature heat exchangers and catalytic reactors in comparison with the current state of the art solutions. In addition to the basic HEX product, the same method will be used to make catalytic reactors by coating the inner walls of the 3-D printed parts with selective catalysts for steam reforming catalytic burner and ammonia cracking applications. Smart sensing will be achieved by incorporating sensors for temperature and heat flux within the body and surfaces of the 3-D printed parts. This will allow for online monitoring, real time optimisation (RTO) and data for the digital twin that is also developed in this project. The final prototype will be integrated into a 12kW high-temperature Solid Oxide Fuel Cell system (SOFC) currently used for the fast-charging of electric vehicles by the implementation partner. The main SME will manufacture the smart HEX solutions for its customers in the high temperature field of SOFC and SOEC.