The 2003 breakthrough discovery of a nanoscale optically active cation channel, channelrhodopsin-2, made it possible for the first time, to genetically re-engineer neuron cells to be photosensitive. It became possible to stimulate or inhibit individual action potentials at will, without further chemical modification. The capabilities have been demonstrated in a number of recent high profile journals detailing optical-neural control from cell culture to primate models. The light-gated cation channels were discovered and first applied by European researchers. The photonics and optoelectronics sectors, which can provide new stimulation technologies to this field, are additionally, European strengths. Nevertheless, in recent years, the dominant research output in this area has shifted to well-funded US laboratories. This proposal therefore aims to create a consortium to develop an array of ultra bright electronically controlled microLEDs which will provide a truly revolutionary tool for the neuroscience and neurotechnology community. The consortium consists of experts in the field who converge the many disciplines (optics, sophisticated LED fabrication, CMOS flip chip design and bonding, biophysics, molecular biology, neurophysiology) to bear on the complex, and crucial to neuroscience, problem of studying dendritic physiology and neural network dynamics. Advances in the techniques of this field will absolutely be required to further our understanding of brain function. The system we propose to develop will be powerful, sophisticated and at the same time, lead to a commercial spin-out that will provide them at relatively low cost. In the longer term, the tools we develop in this proposal will hasten our long term aims of developing an optogenetic retinal prosthesis.