Book excerpt: Electron microscopy techniques are among the most powerful methods for characterization of materials, with the ability to reveal both the atomic-scale structure and composition. This information may be used to elucidate macroscopic properties or to optimize materials synthesis and processing. Instrumentation and techniques for dynamic in situ experiments are undergoing rapid development and have recently been applied to a wide range of problems. This book focuses on time-resolved electron microscopy (including diffraction and spectroscopy), as well as novel instrumentation for temperature and pressure control. In addition to discussing the application of electron microscopy techniques to the in situ study of the kinetics, thermodynamics and mechanisms of reaction, the book also explores their utility as efficient methods of optimizing processing conditions. Imaging techniques featured include: scanning tunneling microscopy, high-resolution electron microscopy, dark field transmission and reflection electron microscopy, Lorentz microscopy, electron holography, scanning and low-energy electron microscopy and photoemission electron microscopy