Optogenetics, a technique to precisely manipulate cell activity by genetically encoded light-sensitive proteins, has been widely and enthusiastically applied as a revolutionary tool in the field of neuroscience. As one of the most representational proteins, channelrhodopsin-2(Ch R2) has been regarded as a prominent tool that contributes to a series of breakthrough in the field of system neuroscience. In this paper, we review the discovery, molecular structure and function of Ch R2. We also review the advanc...