The image quality in electron microscopy often suffers from lens aberration. As a result of lens aberrations, critical information appears distorted at the atomic scale in high-resolution transmission electron microscopy (HRTEM). In scanning TEM (STEM), the spatial resolution of images and the quality of spectroscopic data are greatly reduced. With the recent introduction of aberration-corrected lenses and monochromators, new and exciting images with sub-0.1-nm spatial resolution are now recorded routinely, and electron energy loss data has been used to determine the location of a single atom in an atomic column. As a result of the decreased focal depth of an aberration-corrected lens used in STEM, the dream of three-dimensional (3-D) atomic resolution is one step closer and for HRTEM it was shown that 3-D imaging with atomic resolution is feasible. However, understanding imaging and spectroscopy in HRTEM and STEM still requires refined modeling of the underlying electron scattering processes by multislice image simulation. Since research into the physics and technology of nanoelectronic devices has already moved into sub-10-nm transistor gate lengths, the need for well-understood imaging and spectroscopy at nanoscale dimensions is already upon us. Fortunately, nanowires and other nanotechnology materials serve as useful test samples as well as being potential materials for future nanoelectronics. This enables early development of microscopy methods that will be used to investigate future generations of integrated circuits.