Spatial and phase resolution in electron microscopy

With the invention of the aberration corrector in electron optics, the spatial resolution in electron microscopy has progressively improved and has now reached the sub-50-pm regime, and atomic-resolution electron microscopy has become a versatile tool for investigating the atomic structures in materials and devices. Furthermore, the phase resolution in electron microscopy also exhibits outstanding progress, and it has become possible to visualize electromagnetic fields at atomic dimensions, which strongly contributes to understanding the physical and chemical properties of materials. The electron microscopy society has grown with the improvements in spatial and phase resolutions, and hence, we must continuously develop new hardware, software and methodologies to boost these resolutions. Here, we review the historical progress of spatial and phase resolutions in electron microscopy, where we clarify the definition of these resolutions. We also discuss the future targets in electron microscopy.