One strategy for customizing the properties of some organic polymers and metal alloys involves swapping out their constituent monomers or metal atoms. That type of exchange chemistry, which requires that the constituents be involved in active equilibrium processes, has been exploited by a multinational team led by Zhikun Zheng and A. Dieter Schlüter of ETH Zurich to make a family of two-dimensional metal-organic networks (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja501849y). The team prepared a series of ultrathin samples made up of tri- and hexafunctionalized terpyridine-based monomers joined by Zn2+ ions. The researchers then selectively exchanged the zinc ions with Fe2+, Pb2+, and Co2+. The new materials join the small but growing number of atomically (or nearly atomically) thin materials, such as graphene, boron nitride, and molybdenum disulfide, that are strong enough to be transferred to microscopy grids. These holey supports leave relatively large sections of the films consisting of millions of repeat units suspended over micrometer-sized holes. The mechanical strength of the films and their ability to be isolated and manipulated are essential to using them in molecular electronics, imaging, and other applications.