Hippos produce their own sunscreen from glands beneath their skin—a fluid containing pigments that absorb sunlight in the ultraviolet and visible range.

Hydras appear to be immortal, and each of the aquatic animal's individual cells can rebuild its entire body within days.

The economics of horseshoe crab blood

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

Cow urine, cuttlefish ink, and burned white lead were among the substances used as pigments throughout history.

Mosquito saliva acts as an anticlotting agent

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).

Long strands of sugar molecules in the acidic, digestive fluid of pitcher plants enable the fluid to stretch like chewing gum and trap insects.

Earwax's unusual physical properties help it repel insects in the lab, raising questions about whether it may have evolved to serve that kind of role in animals.

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

Lip balm's core formula has barely changed in 3,500 years, but many of the ingredients added since can actually make chapped lips worse.

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

Honeybees vomit nectar into one another's mouths to transform it into honey

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.

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

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

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.

Why don't giraffes get hypertension?

Polar bears have black skin to better absorb warmth from the sun, but their transparent, hollow hairs scatter and reflect light so that they appear white.

US labs drain an estimated 500,000 horseshoe crabs of blood each year to harvest a compound that screens vaccines and medical devices for bacterial toxins.

Oxygen and nutrients are circulated in tardigrade bodies through physical movement

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.

Bears may have evolved natural mechanisms to prevent blood clots during hibernation, an important development, since inactivity typically leads to blood clots in other animals.

Demystifying sunscreen

Why you have to airlift rhinos upside down

Poison ivy is in the same family as mangoes, cashews, and pistachios, and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

Unlike America's recommendations, Australian authorities don't encourage routine sunscreen use for darker skin tones—reasoning that melanoma risk is low, and it's better to get UV exposure to help the body naturally produce vitamin D.

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.

Studies of tattoo inks have identified over 100 pigments, which have historically included toxic metals but now include organic compounds.

Why 75% of ocean animals glow

To survive underwater hibernation, some freshwater turtles perform cloacal breathing—blood vessels absorb dissolved oxygen from water drawn into the organism's cloaca, or rear orifice.

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it.

From dragon's blood to bone black, explore a timeline of pigments used throughout history, including each pigment's composition, preparation methods, and uses.

Mineral and chemical sunscreens protect differently, but both guard against UV damage.

'Magic ink' is redefining the tattoo

Snake venoms are repurposed proteins responsible for other bodily functions

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

Instead of consuming water and carbon dioxide to produce oxygen and sugar, anoxygenic photosynthesis involves alternative reactants and products.

Odor blockers use nonpolar oils to trap smelly polar molecules

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

Paints are primarily made of pigments from rocks, plants, insects, or synthetic sources, combined with binding agents, solvents, and other potential additives for specific purposes.

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

Kangaroos evolved thick knee cartilage to absorb shock, a feature that scientists are investigating for potential human arthritis treatment and prevention strategies.

Mosquitoes drink a maximum of 0.01 milliliters of blood in a single meal.

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.

Incinerated skeletons, animal blood, and fermented animal waste were among the ingredients used to make the pigments in some of art history's most famous paintings.

Cold-blooded reptiles seek heat, and that behavior may help combat fungal infections

Carboxylic acids are one reason teens are smelly

Poison frogs get their toxins from eating insects and mice

Poison ivy, which produces urushiol throughout the plant, not just in the leaves, can cause year-round rashes.

Zoo animals have developed allergies, too