In this short review, we provide an overview of recent progress in deploying advanced characterization techniques to understand the effects of local inhomogeneities in moir\'e heterostructures over multiple length scales. Particular emphasis is placed on correlating the impact of twist angle misalignment, nano-scale disorder, and atomic relaxation on the moir\'e potential and its collective excitations, particularly moir\'e excitons. Finally, we discuss future technological applications leveraging based on moi\'e excitons.
Comment: Submitted to Small in response to an invitation for the special issue that celebrates the scientific accomplishments of Prof. P M Ajayan