At the atomic frontier of materials science, Nature has gathered the field's attention around two-dimensional perovskites and transition metal dichalcogenides — materials thin enough to rewrite the rules of light, electricity, and quantum behavior. By engineering matter one layer at a time, researchers are discovering that the interface between two materials can be more powerful than either material alone. This collection marks a moment when a discipline moves from curiosity to consequence, inviting the scientific community to document a transformation still very much in progress.