Hierarchical materials. Materials with hierarchical structures represent a promising approach to enhance performance far beyond what can be achieved using composite structures, to add new functionalities and to adapt to special requirements. This issue of MRS Bulletin provides an overview of aspects related to the analysis and development of hierarchical materials. The cover shows an ordered multimodal porous carbon formed through sacrifi cial replication of a preformed multimodal colloidal crystalline template. The hierarchical pore topology, comprised of three-dimensionally ordered macropores with ordered mesopores embedded within the walls, offers large surface area and interconnected pore volume that have been shown to facilitate and enhance mass transport and charge transfer in Li-ion battery anode applications. Image courtesy of the Royal Society of Chemistry (B. Fang, M.-S. Kim, J.H. Kim, S. Lim, J.-S. Yu, J. Mater. Chem. 20, 10253 [2010]). See the technical theme that begins on page 661.