The Massachusetts General Hospital research team that lit up human cells with the help of jellyfish genes a few years ago are back with a more advanced version of the technology. This new version forgoes the complicated external mirror setup in favor of injectable oil droplets impregnated with fluorescent dye. This is the same basic idea as what a team from St Andrews University recently created, except that the plastic bead that served as the their laser's resonating chamber is now an oil droplet. While the technology isn't ready for therapeutic applications just yet, it does hold a great deal of promise. The problem with conventional cellular markers and dye is that they have a broad emission spectrum which can make it difficult to spot the marked cells amidst the rest of the tissue. But with these miniature lasers, doctors will be able to mark and track individual cells no matter where they are in the body. The team recently published their findings in Nature Photonics.