Aberration correction: zooming out to overview.

In the structural characterization of thin specimens by projection (atomic column) imaging, the revolutionary development of aberration-corrected electron microscopy has already brought significant improvements not only in spatial resolution but also in improved image contrast. Some highlights from the symposium are summarized. Despite the purchasing and operating costs as well as the demands they place on operator skills, a staggering number of these new microscopes has already been installed worldwide. Serious challenges, therefore, arise including the need to attract customers from a wide range of disciplines where complex structure problems may require the development of new imaging modes. The ability to image at large scattering angles may be useful in mitigating some of the many as-yet uncorrected delocalization mechanisms that then arise and are systematically identified here. Larger specimen volumes made possible by chromatic aberration correction will benefit the development of more relevant in situ observations, particularly in materials science and catalysis. With additional incorporation of phase shifting electrodes or other devices, these chromatic aberration correctors could also be important for efficient phase contrast imaging in easily damaged biological structures. For many of these formidable problems, earlier experience of the optical microscopy community may teach some lessons.