​This chapter gives an overview of, in the authors’ opinion, the most important developments in the field of zeolite membrane reactors. The chapter is organised based on the approach of structuring these zeolite membrane reactors at different length scales. Common synthesis and characterization techniques are presented and the important role that supports play in the field is examined. Zeolite membranes can work on different length scales; at the reactor level (cm–m), the particle level (mm–μm), or all the way down to the active site level (sub-μm). The membrane can have several functions such as selective feeding of reactants, selective product removal, and/or the introduction of additional catalytic activity. In addition, it can prevent undesired contact of species, e.g. protect the catalyst from poisoning. Although the potential of integrating reaction and separation processes through zeolite membranes is widely ackno​wledged, their widespread application in industry has not yet become reality. Some of the most important hurdles to overcome are discussed, including reproducibility of high-quality membranes, membrane module sealing issues, high cost of support and modules, and scale-up potential. The most recent developments made to overcome these hurdles are reviewed through examples from the literature, which will point out the research trends currently present in the field of zeolite membrane reactors.