The momentum-space structure of electronic wavefunctions affects material response in ways that go beyond band dispersion, and can play an important role in controlling the stability of correlated ground states. In this talk I will discuss how this notion of quantum geometry enters both linear and nonlinear response, and summarize recent progress that have begun to probe these effects in real materials and engineered platforms. I will then describe how a separation of scales can be used to estimate when quantum geometry is expected to matter, and when it can be neglected. Finally, I will introduce cell-natural orbitals and comment on how quantum-geometric effects differ across lattice systems.