In the past few years, scientists have begun to gain the exquisite of controlling the arrangement of matter on the nanometer scale (1 nm = 10−9 m), a new field called nanotechnology, consequently, has started to emerge. As the foundation of nanotechnology, nanostructured materials take on an enormously richer variety of properties and promise exciting new advances in micromechanical, electronic, and magnetic devices as well as in molecular fabrications. The structure–composition–processing–property relationships for these sub-100 nm-sized materials can only be understood by employing the new generation microscopes such as the focused ion beam system in corporate with simultaneous operation of electron beam and in-situ analysis. This book will highlight the principles and vast capabilities of this technique and their applications in this fast-growing nanotechnology field and the challenges in the twenty-first century.