Cochlear implants are currently the standard treatment for profound sensorineural hearing loss. in the last decade, advances in auditory science and technology have not only greatly expanded the utility of electric stimulation to other parts of the auditory nervous system in addition to the cochlea, but have also demonstrated drastic changes in the brain in responses to electric stimulation, including changes in language development and music perception. volume 20 of shar focused on basic science and technology underlying the cochlear implant. however, due to the newness of the ideas and technology, the volume did not cover any emerging applications such as bilateral cochlear implants, combined acoustic-electric stimulation, and other types of auditory prostheses, nor did it review brain plasticity in responses to electric stimulation and its perceptual and language consequences. this proposed volume takes off from volume 20, and expands the examination of implants into new and highly exciting areas. this edited book starts with an overview and introduction by dr. fan-gang zeng. chapters 2-9 cover technological development and the advances in treating the full spectrum of ear disorders in the last ten years. chapters 10-15 discuss brain responses to electric stimulation and their perceptual impact. this volume is particularly exciting because there have been quantum leap from the traditional technology discussed in volume 20. thus, this volume is timely and will be of real importance to the shar audience.