ONLINE COVER RoBeetle Flexes Its Muscle. Untethered, small-scale robots are often powered by miniature batteries with low specific energy (compared with animal fat and chemical fuels). Inspired by the metabolism of animals, Yang et al. developed a robot, called RoBeetle, with size and mass comparable to those of a small insect that achieves crawling locomotion using an artificial micromuscle powered by the controlled catalytic combustion of methanol. RoBeetle can carry payloads up to 2.6 times its body weight, crawl on rough surfaces, and clamber up inclines of 15°. This month's cover is a photograph of RoBeetle on a leaf (see also the Focus by Truby et al.). [CREDIT: XIUFENG YANG AND NÉSTOR O. PÉREZ-ARANCIBIA]