Optogenetic tools have allowed significant advances in the understanding of biological problems, particularly in the neurosciences field. Biological tools as well as optical set-ups have evolved and a wide range of probes and light-controllable modules are now available. The aim of this book is to give a flavour of illumination strategies and imaging with an overview of the different optogenetic tools and their main applications in cell biology. Based on examples covering the different aspects of cell biology, this book provides a practical approach for using light-emitting sensors and light-driven actuators.