This book offers a comprehensive and forward-looking exploration of cochlear implant systems, covering foundational principles such as electrical stimulation, sound coding, and mechanical design, as well as the latest advances in artificial intelligence, surgical robotics, and optogenetics. It connects the dots between technical design and clinical care, highlighting how engineering advances contribute to more effective hearing restoration for cochlear implant patients. While cochlear implants have restored hearing to over a million people worldwide, the knowledge surrounding their design, function, and optimization remains fragmented, spread across engineering literature, clinical studies, and specialized research. This volume aims to contribute toward addressing that gap by unifying these perspectives into a single, accessible resource focused on improving patient outcomes. Written for engineers, clinicians, graduate students, and innovators working at the intersection of hearing science and neurotechnology, the book traces the evolution of cochlear implants from early concepts to emerging technologies. Readers will gain insight into how performance is evaluated in both clinical and real-world settings, and discover how objective measures, computational modeling, medical imaging, and neuroplasticity are driving personalized care. Whether you're developing next-generation auditory devices or seeking a deeper understanding of the science behind cochlear implants, this book serves as both a technical reference and an inspiring guide to the future of hearing restoration for patients.