For several decades, studying the microstructure of materials was quite challenging as most of the research works were theoretical. More importantly, providing direct evidence of atomic scale evolution of material properties was nearly impossible due to the limited analytical tools and techniques. However, with the invention of new analysis and interpretational techniques, elucidating the correlation between material nanostructure and device characteristics has become increasingly important for the development of novel materials. Our research focuses on applying aberration-corrected STEM techniques, emphasizing the unprecedented atomic scale imaging techniques to unravel and understand the material property-dependent device performance at the atomic scale. In-depth investigations of phenomena such as atomic scale visualization of antisite defects (such as those observed in LiFePO4) are tackled.