The most common fish in the sea can make a room glow blue

The lantern fish, of the Myctophidae family, are perhaps the most common fish in all the oceans*, and yet we know little about them. They come from the middle depth of the deep sea and it has been estimated there are a billion metric tons of lantern fish in the world's oceans. They are so-called because they glow like lanterns, usually with a blue light, that shines out in the darkness of the deep. They can control their light organs (called photophores) , dotted around the whole body, with nerves and switch them on and off. They also have large patches of luminous tissue, often around the eyes and the tail, with different patterns for the 300 or so species. The bioluminescent light comes from bacteria which they culture within the organs, but they can control how much light escapes from these photophores. It's thought they use them to 1) counter illuminate their body against the lighter surface waters, making them invisible to prey, 2) as a signal between each other - deep sea explore