This news item is about: New technologies involving optogenetic proteins, which use light to control and observe cells with unprecedented precision, have begun to illuminate processes underlying cellular behavior and the effects of cell and gene–based therapies. Cornell researchers are developing advanced forms of these proteins to form a toolkit to make them more widely available to scientists. With a five year $3.1 million grant from the National Heart, Lung, and Blood Institute, the team will develop the Cornell Heart, Lung, and Blood Resource for Optogenetic Mice (CHROMus), which will incorporate optogenetic proteins in mice and human stem cells. Scientists use such tools to control and observe how different types of cells function and interact.