This year’s medicine laureate Karl Deisseroth transformed the protein channelrhodopsin into a light-controlled switch for nerve cells. Deisseroth introduced the gene for channelrhodopsin into nerve cells from rats. By illuminating the cells with blue light, he was able to trigger a nerve signal. He published this breakthrough in 2005. Two years later, he made this light-controlled switch for nerve cells work in the brains of living mice. #NobelPrize