Title: Revealing the scaling properties of matter through designer low-dimensional crystals

The physical properties of matter change dramatically as atoms assemble into extended solids. Low-dimensional crystals could be used to reveal the intricate evolution of material properties across extremes of scale. However, overcoming profound challenges to progress will require methods for systematic and precise control over the size, shape, and structure of these crystals. To this end, we have developed strategies for controlled crystallization of low-dimensional materials and have identified that even subtle tuning of their dimensionality and morphology yields substantial property changes. Notably, we can manipulate precisely the dimensionality of transition-metal dichalcogenide crystals by growing these model 2D materials on specially functionalized surfaces. The resulting 1D crystals emit light whose energy and profile show an unexpected progression as a function of crystal size. Expanding the scope of our methodologies, we also demonstrate the synthesis of 2D metal-organic frameworks. A reversible 1D-to-2D phase switching can be induced in these molecular frameworks with concomitant and substantial change in electronic transport. Our efforts underscore the importance of rational synthesis in the design of low-dimensional materials that link material lengthscales and advance the fields of optics, electronics, energy conversion, and quantum sensing.