I imagined cells shooting out lasers when I first saw this story, but that isn't quite what it means.
Researchers have found a way to inject cells with oil that captures and bounces light around to create a very specific colour of light. This could be used to label a lot of cells at the same time, so each one would have its own colour and be easier to track. It could even be used to make tumours glow so they can be targeted with light-activated drugs.
It sounds like a sci-fi film to have glowing cells. I love it.