The mesoscale domain, where atomic granularity, quantization of energy, and simplicity of structure and function give way to continuous matter and energy, complex structures, and composite functionalities, represents a new scientifi c frontier. The articles in this issue of MRS Bulletin explore some of the hallmarks of mesoscale science and highlight current and new research directions. On the cover is a mesoscale-structured lightweight honeycomb architecture created by 3D printing of a fiber reinforced epoxy ink by J. A. Lewis and co-workers, where the structures at different length scales can be controlled.
