Optogenetics combines genetic engineering with optics to observe and control the function of cells using light, with clinical implications for restoration of vision and treatment of neurological diseases. As a new discipline much of the basic science and methods are currently under investigation and active development, thus there is a strong need for introductory literature in this field. This graduate level textbook provides an overview of the field of optogenetics in 5 concise chapters: Optogenetic tools, Applications in cellular systems, Mapping neuronal networks, Clinical applications and Restoration of vision and hearing. The concept and content was developed with top international researchers and students at a prestigious Dahlem Conference workshop.