Transient electronic devices. Transient electronics, that can disappear, dissolve, or degrade in a controlled manner over time, has been attracting signifi cant attention as a new and emerging technology. Transient electronics has unique applications, such as bioresorbable medical devices that can provide short-/ medium-term diagnosis and treatment without removal surgery, environmentally friendly devices that can physically decompose and produce no waste, and self-destructing devices that can provide nonrecoverable IT and military security systems. This issue of MRS Bulletin highlights recent progress in transient electronics, focusing on materials aspects, including characterization, fabrication, and applications. The cover shows the dissolution of a transient electronic device comprising an inorganic Si nanomembrane, a Mg electrode, and a SiO2 dielectric formed on a biodegradable polymer, such as silk, poly(lactic-co-glycolic acid) (PLGA), or poly(D,L-lactic acid) (PLA). All materials used for transient electronics are fully degradable into the small molecular scale, and their byproducts are biocompatible and environmentally benign. The inset images demonstrate how a transient electronic device can fully dissolve over time. Main image courtesy of S.-K. Kang, Seoul National University. Inset images courtesy of J. Koo, Northwestern University. See the technical theme that begins on p. 87.