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

With hundreds of ink manufacturers, all unregulated by the FDA, it’s hard to determine the exact ingredients in tattoo inks. Some pigments may contain carcinogenic chemicals, such as heavy metals and aromatic hydrocarbons, or even bacterial contaminants. Red ink often causes allergic reactions and may even contain lead or mercury.

Tattoo ink is injected under the skin, which can leave the body open to infections and allergic reactions. While many tattoo artists are licensed professionals who follow sanitary guidelines, that’s not always the case.

Tattoos last because immune cells trap ink beneath the skin—but there's more to the story. This overview looks at how ancient cultures used tattoos for status, spirituality and punishment; how technology like the electric tattoo machine transformed the art form, and where innovations like smart tattoos could take it next.

Tattoos place ink below the skin's surface layers in packets too large for white blood cells to clear out. By breaking the ink into smaller pieces, the immune system, which is responsible for removing foreign matter, can process them.

Our skin is a fascinating organ that wants nothing more than to protect our bodies from the outside world. Tattoos penetrate that protective wall to inject ink directly into the sensitive, immunologically rich layer of skin known as the dermis.

Tattoos aren’t just a fashion statement. Scientists are trying to find life-saving applications for them. Harvard and MIT researchers are developing tattoo inks that react to body chemicals, alerting diabetics to blood sugar fluctuations or athletes to dehydration. Someday, patients may observe their body chemistry with tattoos that change colors.

One University of Colorado professor has developed an ink that can be "turned on" with exposure to UV light, and "turned off" with sunlight. While the ink could help those who want to hide their body art from family members or coworkers, there are potential uses for medical procedures.

Tattoos place blobs of ink below the surface layers of the skin in packets too large for white blood cells to clear out. By breaking the ink into smaller pieces, they can be processed by the immune system, which is responsible for removing foreign matter.

Although tattoos are fairly common in the US, some taboos remain. A 2017 study in the Journal of Social Psychology found discrimination against tattoos is alive and well, and that even individuals with tattoos associate them with negative stereotypes.

Tattoos have waxed and waned in popularity over the centuries, depending upon the social standing of their wearers. Throughout US history, they were often considered taboo. However, growing acceptance of tattoos means they’re more visible in the public eye.

“Tatatau” roughly translates to “strike,” a reference to the ancient process, which involved tapping ink into the skin with sharpened objects, like the bronze implements used circa 1450 BCE in Egypt, below.

An increasing number of Americans, including high-profile celebrities, get tattoos removed because laser removal has become more advanced and cost-effective. The tattoo industry is adjusting to this mainstream trend.

In the slow method, artists use needles to puncture the skin. Then, pigmented thread is drawn through the punctures to create the tattoo, resembling embroidery in the flesh. The method is experiencing a cultural revival within Canada’s First Nations communities.

About a quarter of the world’s agricultural products are contaminated with mycotoxins. Some of these compounds can cause serious health problems, including cancer, so the US government has set up monitoring programs to detect them in our food and in animal feed. Humans can become ill if they eat contaminated food, but also if they ingest products from animals that had previously consumed these toxic compounds, such as milk from a cow that ate contaminated corn.

What if you could see your tattoos before they’re embedded in your skin? Or take a virtual visit into a local studio to work out your nerves over a first tattoo? The industry is anticipating some big technological changes, from 3D designs to sci-fi upgrades to more precise tattoo guns.

Around 450 BCE, Scythians inhabiting what is now southern Siberia were recorded as wearing tattoos of swirling mythical beasts to signify nobility. At the same time, tattoos have identified lower-status and enslaved people.

Industrial alcohol was still legal during Prohibition, and was often used by bootleggers. In an attempt to disrupt the black market, the government required toxic additives to be included in industrial alcohol, leading to more than one death.

Consumer Reports' tests of more than 20 supplement powders and shakes in 2025 found that more than two-thirds of them contain unsafe levels of lead. Some contained 10 times the amount of lead that's considered acceptable to ingest in a day. The levels they found, in some cases, were even higher than when they tested the products 15 years earlier.

Besides the various salts and metals used to produce fireworks colors, shells are also filled with gunpowder and oxidizers to help fuel and accelerate reactions. Chlorates help strengthen colors, while dextrin, a starch, helps hold mixtures together.

These devices use diodes and mirrors to create pulses of light that vaporize metal in billionths of a second, though at wavelengths that cannot react with organic material. Pulse width, power, and speed adjustments can produce white, black, and even colored patterns through controlled heat reactions.

Titanium white can be found in items ranging from paint to pills. Though it was created in New York in 1908, the pigment was first used hundreds of years earlier by the Inca, according to this article.

Lead was one of the earliest metals mined on Earth, desired for its soft malleability and used in cosmetics, pipework, gasoline, and more. But even though researchers demonstrated its toxicity in the 20th century, much of the world still uses it.

Sailors often come home with mermaids or turtles adorning their bodies. But what does it mean to have permanent images of propellers on your bum, British galleons with soaring tiers of sails on your chest, or a bicep portrait of the Roman god Neptune? Those tattoos represent meaningful naval milestones.

Through a series of processes that collectively make up phytoremediation, plants can take up pollutants from soil and water through their roots, then break them down, release them as less harmful gases, or store them within their cells. Any plants that sequester heavy metals or other toxins must be removed and managed after the environment is decontaminated.

Ötzi the Iceman, discovered in 1991, is one of the oldest human mummies ever found—and his 61 tattoos remain a mystery. This explainer looks at how researchers believe the tattoos were made, what their placement suggests about ancient medicine and culture, and why we’re still piecing together their true purpose today.

Most modern processed foods rely on a number of preservatives to stay fresh from production to our plates. The most common include citric acid (preservative and flavor), sodium benzoate (preservative), xanthan gum (thickening and stabilizing), carrageenan (thickening), and red dyes 3 and 4 (for color).

Previously used to map the distribution of molecules on biological tissue samples, researchers combined the technique with machine learning to uncover six layers of pigments, binders, and a thin gold leaf layer within The Marriage of the Virgin, from a collection in the Metropolitan Museum of Art. The technique may help identify and track artists' material use to learn about pieces of unknown provenance.