While swimming off the coast of Puerto Rico, the water glows with every stroke. Every stroke through the clear water left a wake of white-ish blue light. This was caused by tiny organisms, known as dinoflagellates. On a warm summer night, lightning bugs fly around sporadically glowing in the dark. A jellyfish swims through the ocean, glowing as it makes it way around. How do they do that, it’s so cool! The answer is that these organisms all contain proteins, which produce bioluminescence, which is a natural phenomenon, in which living organisms convert chemical energy into light energy.
In 1962 scientists identified two proteins which allow organisms to glow, one produced blue light while the other—green fluorescent protein, or GFP—turned that blue light a brilliant green. GFP has been used to tag genes and cancer cells, so that they can be tracked throughout the body. But what is really cool is that scientists have inserted the GFP into different animals, such as mice, rabbits, cats, pigs and dogs, so that they too can glow in the dark! 
Follow the link and heck out this video to see a glow in the dark mouse! It’s awesome!