Tetrachromacy allows humans to observe 10 times the normal amount of colors

Proteins with limited light sensitivity prevent humans from seeing all types of light

Specialized photoreceptor cells in the retina called cones each possess photopigments that activate when exposed to three ranges of visible light. Other forms of electromagnetic radiation outside the activation range do not generate signals for processing in the brain, thereby limiting average human vision to approximately 10 million colors.

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

While some animals are sensitive to many forms of light, humans possess receptors that are sensitive to red, green, and blue wavelengths. These receptors send signals to the brain, which are processed and mixed to produce the array of colors we observe, including magenta, pink, and "supercolors" that lack a corresponding natural wavelength in the visible spectrum.

Here’s why genetically identical sisters can have different colored eyes

The sequence of DNA that we inherit from our parents encodes directions for making our cells and giving us specific traits. Identical twins have the same DNA sequence, so how can one twin end up with a genetic disorder while the other twin does not? Robin Ball explains how the secret lies in X chromosome inactivation.

Color originates from the brain processing light of varying wavelengths

Various geometric models, including Newton's color circle of hue and saturation and the horseshoe-shaped XYZ space for mixing colors via vector mathematics, have been proposed to describe colors accurately. However, these models do not encapsulate the variety of psychological effects that cause perceived colors to differ from mathematical representations.

Brain implants can help colorblind people hear colors

Colorblind artist Neil Harbisson was born into a world of grey. In 2004, he had a chip installed connected to an external color frequency sensor. Once the sensor "reads" a color, it sends a signal to the chip and plays an associated sound both in and outside Harbisson's head.

Modern genetic testing stems from a 1950s discovery about the cause of Down syndrome

Scientists found that an additional copy of chromosome 21 causes the disease and developed an approach to stain chromosomes so they could be manually sorted and counted, which is called karyotyping. The breakthrough discovery by Marthe Gautier, a young French doctor and cytogenetics researcher, was appropriated by a male colleague, who listed himself as the lead author of the study reporting the finding.

What is the rarest color in nature?

Plants, animals, or minerals found in nature bear almost every color imaginable. There are two factors that influence what hues you see in the wild: physics and evolution. So, which colors are you least likely to see in the natural world? Victoria Hwang explores one of nature’s rarest spectacles.

Synchrotron radiation has revealed the fur color of creatures millions of years old

When electrons are accelerated in the loop, they produce intense X-rays that can reveal properties of a sample struck by them, just as X-rays can be used to show bone structure in humans. Studying the reflected light from fossils can uncover the presence of known pigmentation compounds.

Usher Syndrome, a rare genetic disorder, causes progressive hearing and vision loss

People with one of the subtypes of this condition have a genetic mutation that starves cells in the inner ear and the retina of proteins required for detecting sound and light. Gene therapy in animals has seemed like a promising treatment for the condition.

Examining self-diagnosed synesthesia

A growing number of people on social media claim to have a perceptual condition that lets them smell colors, see music, or taste sounds. But do they really?

Organisms can possess multiple unique sets of DNA in one body

Genetic chimeras can result when cells with different DNA combine, such as when two sperm cells fertilize two egg cells, creating two embryos that then merge. In mosaicism, mutations arise within an organism after conception and can spread through cell division, resulting in diseases and forming genetically distinct anatomy.

Half of human DNA is inherited from each parent

Within most cells reside 23 pairs of chromosomes made of tightly wound DNA, and half of each pair is inherited from each parent. The 23rd pair consists of two X-shaped chromosomes, or one such chromosome paired with a Y chromosome, and determines biological sex.

Humans may be able to distinguish more than one trillion scents

That's according to one estimate published in 2014. This figure far exceeds earlier estimates of a human smelling ceiling around 10,000 odors. The newer figure is derived from experiments in which volunteers agreed to sniff varying scents. Researchers mixed odor components and had volunteers sniff the brews to detect subtle scent differences. (Some users may experience a paywall.)

Alkaptonuria was the first identified genetic disorder

In 1902, a rare recessive mutation was determined to cause alkaptonuria—a disease that induces dark pigmentation of connective tissue. The responsible gene was not isolated until the 1990s.

She can't feel pain, hunger, or danger

Olivia Farnsworth, born with a rare chromosome 6p deletion, may be the only person known to lack pain, hunger, and fear responses. This overview explores her unique condition, the incredible incidents that revealed it, and how scientists hope her case could unlock new insights into human survival and sensory systems.

Restoring vision in impaired patients via CRISPR

Since CRISPR was revealed as a gene editing tool in 2012, it has been on an accelerated track to real-world applications. Among other clinical demonstrations, doctors have now injected a CRISPR treatment directly into eye cells, helping vision-impaired patients see shapes and colors again.

Each taste bud has 10 to 50 sensory cells that form a flower-like capsule

At the top of the structure are thin filaments known as "taste hairs" that bind taste-producing substances to the surfaces of the cell, after which corresponding electrical signals are sent to the brain. Adults have 2,000 to 4,000 taste buds on their tongue.

Cats have a mutation preventing them from tasting sugar

When certain tastes (sweet, umami, bitter) become irrelevant due to a species' diet or lifestyle, the genes for those tastes degrade. In felines, scientists believe a shift to a protein-heavy diet put evolutionary pressure on the genes responsible for tasting sweetness. (Some users may encounter a paywall.)

Humans won't develop more than 5 fingers because it would impact too many body parts

All modern animals have five or fewer digits on each of their limbs. Roughly 348 million years ago, at least two species had eight: the Ichthyostega and the Acanthostega. According to Dollo's law, complex evolved features are very unlikely to recur in evolution. Researchers believe humans won't develop more than five digits because it would impact other body parts too much.

The ultrarare 'Er' blood type has been documented only about 40 times

In 2022, the tragic loss of a pregnancy led researchers to the discovery that the rare "Er" blood type could potentially cause a mismatch in blood types between mother and fetus during pregnancy, with devastating consequences. (Some users may encounter a paywall.)

The body's master clock has 20,000 neurons

The suprachiasmatic nucleus, the master clock in mammals, has 20,000 neurons that help maintain the light-dark cycle in the body. Among its jobs: It receives light input information from the retina and then signals peripheral body clocks to act on this information, driving everything from body temperature to hunger.

Caucasians are at the greatest risk of developing macular degeneration

A 2016 analysis across ethnic groups found, among other things, that white participants had the highest incidence of the disease, followed by Chinese, Hispanic, and Black participants. This study did not answer why that may be the case.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens

This type of extreme reaction to harmless holes, dots, cracks, and seed collections can be debilitating for those who have it, but it is not an officially recognized disorder in the DSM-5.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

How David Attenborough's work in color television gave tennis balls their color

As controller of BBC Two, Attenborough wanted the BBC to achieve the first full-color broadcast in Europe and saw Wimbledon as the perfect event to make it happen. Noticing that the white tennis balls used then would stain green and become less visible on color broadcasts as matches progressed, he suggested fluorescent balls, which were eventually adopted.

Roughly 1 in 125 people have autism spectrum disorder globally

The disorder has been increasingly diagnosed as its definition has grown broader and as clinicians have become more adept at identifying it—with some estimates suggesting the figures are much higher. These figures include people across the spectrum, some of whom live mostly independent lives, while others require life-long care and assistance.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Dorothy's famous entrance into Oz in 'The Wizard of Oz' relied on analog tricks, including a body double and sepia-toned paint, as much as it did on technology

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

See a 3D reconstruction of Tenochtitlan, the Aztec capital that was home to an estimated population of 200,000 to 400,000.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

After her fellow cult members tried to kill her with an LSD-infused hamburger, one member of the Manson Family, the murderous cult led by Charles Manson, decided to testify against the group's leader.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Fast-casual restaurant Chili's is experiencing a resurgence, with its parent company recently reporting a nearly 32% increase in sales, thanks to passionate Gen Z fans on TikTok.

Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity, where it was purposefully grown in the English royal gardens at Kew, the Faculty of Medicine in Paris, and a few other locations.