The sensory receptors which belong to the vestibular and auditory systems of vertebrates are termed as hair cells. They are present within the ears. These cells are able to detect movement around them through mechanotransduction. In mammals, hair cells are located in the cochlea of the inner ear. These cells can be categorized into two types, the inner and outer hair cells. They are functionally and anatomically different from each other. The inner hair cells are responsible for converting the sound vibrations in the fluids of the cochlea into electrical signals which are then conveyed to the brain. They are unable to regenerate. Therefore, any injury or damage to them is permanent and can lead to a decrease in hearing sensitivity. This book covers in detail some existent theories and innovative concepts revolving around the regeneration, repair and death of hair cells. Its aim is to present researches that have transformed this discipline and aided its advancement. This book will help the readers in keeping pace with the rapid changes in this field.