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This chapter reviews the use of scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) to understand the phase presence and microstructure of hafnia ferroelectrics. These aspects of the films govern the properties, but they are challenging to interrogate due to the multiple interrelated phases and small grain sizes. As such, STEM and TEM have proven to be invaluable tools in various efforts that have sought to explain different aspects of ferroelectricity in hafnia. We review how these methods have been utilized to characterize the general capacitor structures, the phases present, and the different aspects of film microstructure and film nonuniformity. We discuss the influence of these findings on the properties of hafnia ferroelectrics.