These mice are glowing because scientists inserted a gene found in certain bioluminescent jellyfish into their DNA. That gene is a recipe for a protein that glows green when hit by blue or ultraviolet light. The protein is present throughout their bodies. As a result, their skin, eyes and organs give off an eerie light. Only their fur does not glow. But the organs give out such a bright light that the light from the organs can be seen through their skin so you can see it.