Structured catalysts and reactors have been becoming significant process intensification technologies in gas-solid and gas-liquid-solid reactions due to the unique advantages that they offer in hydrodynamics, transport phenomena, and reaction kinetics in comparison with traditional pellet packed-bed reactors. Because of this, a multi-disciplinary study on structured catalysts and reactors is emerging involving chemistry, chemical engineering, environmental engineering, energy engineering and powder engineering. This is rarely encountered in other research fields. In practice, monolith structures have been widely used to deal with automobile exhaust gases, flue gas from power plants, catalytic combustion, etc., while open cross-flow structures were the earliest in the family of structured catalysts and reactors to be used in chemical engineering for catalytic distillation at large scale, which, of course, can be extended to other countercurrent or concurrent operations, coupling reaction and separation. In addition, structured microreactors can be used to produce nanoparticles as well as fine chemicals. We anticipate that more applications will be exploited in this exciting field. From the scientific viewpoint, it is still required for chemists to explore the structure-performance relationship at microscopic scale soas to find new catalytically active species and substrates. On the other hand, also the structure-performance relationship at macroscopic scale should be considered from an engineering viewpoint due to the regular arrangement of structured catalysts/reactors in nature. The study on the design, operation and optimization of structured catalysts and reactors is also necessary to develop mature technology for future applications.