Electron microscopes are used in most investigation methods in materials science and are key players in the rise of nanotechnology. As the limits of electron microscopy are being pushed by the development of much-improved electron sources and electron optics, the attention of the electron microscopy community is turning towards imaging electron detectors, but the literature on this complex field is limited and extremely fragmented. This book provides a comprehensive introduction to electron detectors, bringing together the most important achievements and highlighting the most important advances. It discusses theoretical, technological and functional aspects of electron detectors, building a natural progression through the main concepts in detection as well as providing an excellent resource for teaching and for new researchers in electron microscopy. The book also presents a critical outline of the new generation of electron detectors, which highlights the latest breakthroughs and illustrates how these will further push the limits of electron microscopy.