Liquid-phase exfoliation of graphene has opened new avenues for the large-scale production of a wide range of 2D materials, including Transition Metal Mono- and Dichalcogenides. These materials, along with layered double hydroxides and novel layered materials such as MXenes, have demonstrated exceptional performance in energy storage (batteries, supercapacitors) and conversion (catalysis). Structural and morphological features and the presence of defects can either enhance or degrade their properties. On the other hand, this can also proactively be used to achieve certain functionalities using defect engineering. In this presentation, I will discuss various case studies highlighting the energy performance of 2D materials, and how aberration-corrected STEM techniques, combined with density functional theory, provide valuable insights into structure-property relationships. Atom-by-atom characterization is crucial for identifying and understanding the configurations of point defects, their mobility, and their influence on the electronic properties.