High performance dielectric capacitors are ubiquitous components in the modern electronics industry, owing to the highest power density, fastest charge–discharge rates, and long lifetime. However, the wide application of dielectric capacitors is limited owing to the low energy density. Over the past decades, multiscale structures of dielectric ceramics have been extensively explored and many exciting developments have been achieved. Despite the rapid development of energy storage properties, the atomic structure of dielectric materials is rarely investigated. In this paper, we present a brief overview of how scanning transmission electron microscopy (STEM) is used as a tool to elucidate the morphology, local structure heterogeneity, atomic resolution structure phase evolution and the correlation with energy storage properties, which provides a powerful tool for rational design and synergistic optimization.