Resistive switching phenomena in thin films: Materials, devices, and applications. This issue of MRS Bulletin starts by reviewing some of the promising applications of resistive switching phenomena in thin-film devices, and then follows with the detailed discussion of current state-of-the-art understanding of the physics behind this phenomenon in several major classes of material systems. The cover shows a 17 × 17 crossbar array of 50-nm-thick TiO2 memristors defined by 50-nm-wide platinum electrodes spaced by 50 nm gaps. (Image courtesy of J. Joshua Yang, G. Medeiros-Ribeiro, and R. Stan Williams of Hewlett Packard Labs.) A schematic illustrating a crossbar array memory circuit with a unit cell size of 100 × 100 nm2, fabricated by a direct metal-transfer process, is superimposed on the right (adapted from Kim et al., Adv. Mater., 23, 2104 [2011]). See the technical theme that begins on page 108.