Underwater Creature

There are also cases deep-sea creatures being abnormally small, such as the lantern shark, which fits in an adult human's palm.
Bioluminescence
Bioluminescence is the ability for an organism to create light through chemical reactions. Creatures use bioluminescence in many ways: to light their way, attract prey, or seduce a mate. Many underwater animals are bioluminescent—from the Viper fish to the Flashlight fish, which is named for its light. Some creatures, such as the angler fish have a concentration photophores in a small limb that protrudes from their bodies, which they use as a lure to catch curious fish. Bioluminescence can also confuse enemies. The chemical process bioluminescence requires at least two chemicals: the light producing chemical called luciferin and the reaction causing chemical called luciferase. The luciferase catalyzes the oxidation the luciferin causing light and resulting in an inactive oxyluciferin. Fresh luciferin must be brought in through the diet or through internal synthesis.