This two-laser, one fiber system is optimal for doing utilization of the blue-light activator channelrhodopsin-2 and/or the yellow-light inhibitor halorhodopsin (and future derivatives thereof) at the same time. In this way, bi-directional control of a single point in the brain can be performed, using ‘optogenetics’ technologies. This setups saves thousands of dollars, and is more flexible and powerful, than commercial single-color fiber-coupled lasers. In addition, the setup can be used (carefully) in an MRI-compatible fashion.