One of the tenets of nanoscience is the study of systems whose properties change with size. The image of several vials lined up with quantum dot solutions glowing from red to blue is emblematic. Less familiar is the case for chemical reactions. If you carry out your reaction in a 500 μl or in a 10 ml flask the outcome is going to be the same. But if you start decreasing the size of the vessel to a point in which the interaction between the walls of the container and your molecules becomes relevant, then the size of the container will play a role in your chemistry. In this issue, we publish a Review Article highlighting various size effects in chemistry.

Chemistry under a nanoconfined space is not a conceptually new proposition. Zeolites, for example, are used routinely to catalyse and control the outcome of oil cracking reactions in industry. In academia, studies of reactions within micelles and macromolecules date back to the 1970s. In biology, nanoconfinement is the key reason for the selectivity of enzymatic reactions. Recently, however, the field has expanded significantly, showing an ever-increasing level of sophistication. The size and shape of zeolites can improve the stereoselectivity and the yield of bioplastics production by preventing racemization and the formation of side products. Containers can be engineered to pre-organize reagents next to a catalytic site for enhanced reaction rates. Containers can even be made to assemble and disassemble by means of a physicochemical signal; in this way, the formation of a certain desired product can be triggered at a specific moment in time. Nanocontainers are also useful to isolate and study reactive intermediates with immediate benefits in the design of more efficient catalysts; such is the case for catalysts whose activity is similar to that of natural enzymes (so-called, nanozymes) that aim to marry the kinetics of natural enzymes with greater substrate versatility.

Another important reason to study chemical reactions under nanoconfined spaces is the direct role compartmentalization of biochemical reactions plays in the machinery of life. If we wish to understand life, out-of-equilibrium systems and make materials with life-like behaviour, chemistry under nanoconfinement remains a frontier to be conquered.