Introduction. Optogenetic is an experimental technique that combines genetic engineering and optical physics procedures to mark specific neurons in the brain and activate them at will through rays of light of certain frequency. Aim. To explain, to readers not versed in genetics the history, the rationale and the present and future applications of optogenetic in brain and mental processes research. Development. The current development of this technique is allowing considerable advances in accurate knowledge about the neural circuits that control behavior and motivational and cognitive states, like hunger and thirst, pain, sleep or learning and memory. Among the first shocking results there are the creation and control of false memories. Conclusions. The optogenetics is a revolutionary experimental technique called to replace some of the classics techniques in brain behavior research and an important way in the development and control of mental processes and in the treatment of their diseases.