Some organisms can change color by quickly revealing or hiding various pigments, as seen in octopuses, squids, and other cephalopods.

Some octopuses change color while they sleep, potentially in response to dreaming about hiding, hunting, or other activities that involve changing color while awake.

Chameleons change color by altering the spacing of nanocrystals under their skin, which changes what colors of light are absorbed and reflected.

Starting with red, colorful objects will appear to lose their colors the deeper they are submerged because water scatters light, reducing the amount available to reflect off objects and be observed.

Biofluorescent animals—those that absorb light, such as ultraviolet rays, and re-emit other types of light, such as neon green—include some flying squirrels, scorpions, sea turtles, and platypuses.

Blood can be blue, green, magenta, or transparent due to differences in the oxygen-carrying respiratory pigments they contain.

Some corals absorb harmful ultraviolet radiation and re-emit it as visible light, thereby protecting symbiotic algae within their tissues and providing them with energy for photosynthesis.

Coral reefs get their colors from zooxanthellae—photosynthetic algae that line corals' digestive tracts and provide them with sugars in exchange for a home.

View a gallery of biofluorescent animals, which contain cells that emit various colors when exposed to ultraviolet light.

Corals sacrifice their food source and expel colorful microorganisms to protect themselves during coral bleaching—a phenomenon that resembles an organism's immune system attacking itself.

In the 1950s, Alan Turing developed a mathematical model to explain why animals have stripes, spots, and other patterns based on differences in how quickly two interacting chemicals spread throughout a developing organism.

As immobile animals, corals and the organisms that live on them have evolved a suite of chemical compounds to prevent disease and ward off predators they cannot outrun.

View illustrations of bioluminescent functions in marine organisms

Why 75% of ocean animals glow

Bioluminescent organisms produce their own light through chemical reactions involving unstable, energetic molecules, while biofluorescent organisms almost immediately re-emit light shone on them, but at a different wavelength.

View a gallery of bioluminescent organisms, including snails, worms, fungi, jellyfish, and mushrooms.

Massive blooms of microscopic algae called dinoflagellates produce the neon blue light seen in glowing tides.

Not all colored materials can become pigments—the process of grinding materials down into smaller particles may destroy the color-producing molecules.

Water is naturally tinted with a slight blue, but sediments and organics can alter its color

Bioluminescence became common in the ocean to support survival in dark environments

Octopuses have taste receptors along their tentacles

Humans can distinguish about 10 million colors—a number that is limited by photopigments that only activate when exposed to specific wavelengths of light.

Fossilized pigment granules have enabled scientists to deduce the colors of long-extinct organisms, including dinosaurs.

The first appearance of bioluminescence was at least 540 million years ago

Research has found that when their symbiotic algae are not producing oxygen via photosynthesis, corals twirl hairlike structures to circulate water and draw oxygen into their outer tissues.

Blood color differs across the animal kingdom, with some animals producing blood that appears green (a group of lizards in New Guinea) or blue (horseshoe crabs).

Evolution doesn't want you to see these animals

Elysia chlorotica is a sea slug that can photosynthesize, making it an animal with the defining ability of a plant.

Creating a perfect red pigment that is vivid, durable, and nontoxic is likely impossible.

Meet Cystisoma, the 7-inch crustacean with eyes for a head

When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

Some organisms are composed of a single cell visible to the naked eye

View examples of luciferin, the light-emitting molecule behind bioluminescence

Divers capture a blanket octopus unveiling her billowing membrane

Electrogenic animals generate their own electricity by changing the pattern of electrical charges in disc-shaped cells called electrocytes.

Violet is the rarest color in nature because it is the most energetically demanding visible light for pigments to reflect and for nanostructures to scatter.

View a gallery of animals found on abyssal plains, hydrothermal vents, seamounts, and other deep-sea habitats.

Named after the Ancient Greek term for 'eight-footed,' octopuses have eight, suction-filled arms, not tentacles—the latter only feature suckers at their tips.

Because it is observed in organisms that are not closely related, biofluorescence is thought to have emerged independently many times in nature—over 100 in fish alone.

When processing light, the brain can perceive colors with no natural wavelength

Over 1 million fish, marine mammals, and invertebrate species depend on coral reefs for habitats, camouflage, and food.

Behind the fascinating disguising mechanism of camouflage

Bioluminescence provides organisms with a method of hunting, defense, or mating

Coral reefs are built by thousands of coral polyps—tiny animals whose mouths both consume food and expel waste.

Flamingos get their pink color from pigments in their food, but they cannot be any color because their bodies cannot process every type of pigment.

Catfish have taste buds spread across their entire skin, making their whole body function like a tongue that can taste food several feet away.

Sea stars are invertebrates—they lack a backbone—and while most exhibit pentametric radial symmetry due to having five arms radiating from a central disk, some can possess more than 40.

Blacklights can illuminate certain biological materials, including blood, teeth, and fingernails, because they contain fluorophores—molecules that visibly glow immediately after exposure to higher-energy light.

View a gallery of microscopic images of butterfly wings, revealing colorful layers of scales, hairs, and metallic-looking structures.

Meet siphonophores, breathtaking jellyfish-like organisms

Scientists can tag distinct proteins with fluorescent probes that emit different colors, allowing them to visualize multiple biochemical processes simultaneously.