This article reviews current progress in research in ferroelectric switching
phenomena using in situ electron microscopy. We focus on
state-of-the-art instrumentation, analytical methods, experimental procedures,
and image contrast mechanisms. Particular emphasis is on ferroelectric domain
and domain wall structures that determine ferroelectric behaviors. The
applicability of in situ microscopy to studying a wide range of
switching phenomena, such as domain nucleation, domain wall motion, and domain
wall pinning by various types of defects, in ferroelectric thin films is
demonstrated. The underlying physics of these dynamic processes is also
discussed.