According to the New Scientist Inventions blog (one of my new favorite web hangouts), the National Institute of Environmental Health Services is attempting to create fish that'll light up like fireflies when swimming through polluted waters. Because fireflies glow when an enzyme in their stomach oxidizes, the NIEHS hopes to implant those same traits into the eggs of zebrafish. Then, other genes would be manipulated to make the fish sensitive to specific pollutants. As a result, the fish could glow in the presence of mercury, indicating to scientists just how impure the water is. Crazier still, the intensity of their glow could be an even more telling factor: the brighter the glow, the worse the pollution.