The key mol­e­cule of opto­ge­net­ics is a light-sensitive pro­tein called chan­nel­rhodopsin, which is extract­ed from green algae. Scientists can insert chan­nel­rhodopsin into mem­o­ry cells. Subsequently, sci­en­tists can even acti­vate the­se with blue light which they deliv­er deep inside the brain with optic fibers.