The circle inside each cell is its nucleus. As this video begins the circles are bright, which reveals the presence of inactive kinase protein decoys. After the Stanford bioengineers stimulated the cells to activate the kinases, the nuclear circles darkened again. Kinase proteins regulate health and help cause disease. So creating a way to track these light and dark areas allows researchers to see whether a kinase is active or inactive when a cell is healthy or diseased. This new technique could speed drug discovery.