With its atomic thinness and outstanding electronic and mechanical properties, graphene stormed the materials research world about five years ago, repeatedly grabbing headlines in the mainstream and scientific press alike. Large numbers of scientists set about probing this one- or few-atoms-thick form of carbon and devoted themselves to developing its applications. Clearly, this nearly two-dimensional (2-D) material is fascinating. But when it comes to atomically thin or nearly atomically thin materials, graphene isn’t the only game in town. The past few years—and especially the past few months—have seen several materials, including boron nitride, molybdenum disulfide, metal carbides, and others, join the 2-D club. Researchers are investigating the fundamental properties of these materials and devising methods for preparing them in large quantities. One of the main goals of this work is to exploit the chemical, electronic, and other unique properties of this group of ultrathin materials for applications f...