The ion channels, transporters and metabotropic receptors that underlie neuronal activity can be seen as molecular machines that are amenable to functional manipulation. One of the most rewarding functions to add is sensitivity toward light. Our group has succeeded in photosensitizing several ion channels, such as glutamate receptors and voltage-gated potassium channels using a combination of synthetic chemistry and protein engineering. In addition, we have developed .reversibly caged. versions of glutamate and other neurotransmitters. I will discuss the principles that underlie the design of artificial photoreceptors and photochromic neurotransmitters. In particular, I will address our systematic studies on their dynamic properties, which are of crucial importance for their biological applications. The use of our hybrid photoreceptors in cultured neurons, brain slices, and intact animals (e.g. zebrafish, leeches and mice) will be shown and the role of these systems in the elucidation of neural circuitry and the restoration of vision will be discussed.