Imagine a place so dark you can't see the nose on your face. Eyes opened or closed, it's all the same because the sun never shines there. Up ahead, you see a light. When you creep in to investigate, a blue light flits around you. "I could watch this forever," you think. But you can't because the mouth of an anglerfish has just sprung open and eaten you alive. You are just one of many creatures at the bottom of the ocean who learn too late to appreciate the power of bioluminescence. Bioluminescence refers to the ability of certain living things to create light. The human body can make stuff like ear wax and toe nails, but these organisms can turn parts of their body into glow sticks. It's like nature made them ready to rave. Why? In one way or another, bioluminescence improves a living thing's chances of survival. Take the firefly. It's ability to glow green helps it attract a mate on a warm, summer night, but it's just one of many living things that can glow. The railroad worm, Phrixothrix hirtus, can light up its body in two colors: red and green. Would you eat something that looks like an airport runway? Neither would any sensible predator. The flashing lights keep the worm safe. Then there's the deep sea shrimp, Acantherphyra purpurea. When it feels threatened, it spews a cloud of glowing goo from its mouth. Who doesn't run the other way when they've just been puked on? Plus, that puke attracts bigger predators who want to eat the shrimp's enemy. So what if you can't bioluminesce? No problem! There are other ways for living things to make bioluminescence work for them, even if they weren't born with the equipment to glow. Let's revisit the anglerfish moments before it tried to eat you. That glowing bait on top of its head? It comes from a pocket of skin called the esca. The esca holds bioluminescent bacteria. The anglerfish can't glow there by itself, so it holds a sack of glowing bacteria instead. Remember the firefly? It can actually make itself glow. Inside its lantern are two chemicals, a luciferin and a luciferase. When firefly luciferase and luciferin mix together in the presence of oxygen and fuel for the cell, called ATP, the chemical reaction gives off energy in the form of light. Once scientists figured out how the firefly creates its luciferase and luciferin, they used genetic engineering to make this light-producing reaction occur inside other living things that can't glow. For example, they inserted the genes, or instructions, for a cell to create firefly luciferase and luciferin into a tobacco plant. Once there, the tobacco plant followed the instructions slipped into its DNA and lit up like a Christmas tree. The beauty of bioluminescence, unlike the light from the sun or an incandescent bulb, is that it's not hot. It takes place in a range of temperatures that don't burn a living thing. And unlike a glow stick, which fades out as the chemicals inside get used up, bioluminescent reactions use replenishable resources. That's one reason engineers are trying to develop bioluminescent trees. Just think, if planted on the side of highways, they could light the way, using only oxygen and other freely available, clean resources to run. Talk about survival advantage! That could help our planet live longer. Do you find yourself thinking of other ways to put bioluminescence to good use? That glow stick you swing at a rave may help you find a mate, but how else can bioluminescence improve your survival? If you start thinking in this way, you have seen the light.