By now you know how important it is to get sun exposure for vitamin D production. Now researchers at Georgetown University Medical Center have found that sunlight energises T-cells that play a central role in human immunity. Their findings suggest how the skin, the body's largest organ, stays alert to the many microbes that can nest there. They specifically found that low levels of blue light, found in the Sun's rays, makes T-cells move faster. If blue light T-cell activation has only beneficial responses, blue light therapy could be used to boost immunity for patients with compromised immune systems. We may very well see this technology used alongside cancer treatments in the near future.