Highly charged ions are key research objects in atomic physics. Precision spectroscopy of such ions provides a powerful tool for exploring relativistic and quantum electrodynamics effects. Additionally, the interaction of high-energy heavy-ions with matter is itself a topic of importance in many areas of applied physics, including fusion and plasma physics, accelerator physics, materials science and semiconductor device preparation and behavior. This work provides a complete overview of modern methods of studying highly charged ions. With chapters covering everything from the essential background physics to theoretical description and industrial applications, the wide range of international contributors have created a single volume covering essential physics needed by those who study or use these ions.