These cells 'taste' danger, trigger immune responses

How bitter taste receptors help guard against infection

Receptors for "bitter" tastes evolved to detect potentially harmful plant chemicals, such as nicotine. The receptors also trigger bacteria-fighting responses, including waving hairlike projections to bat away bacteria, ordering the release of bacteria-killing nitric oxide, and calling for antimicrobial protein reinforcements.

Taste buds are found throughout the body, with different biological functions

As biological structures, taste receptors take in molecules, analyze them, and send signals to the brain letting us know what they've found. This functionality makes them useful throughout the body, most notably in the gut where receptors act as glucose sensors.

Many parts of the body, including the testicles, have bitter, sweet, and umami receptors

Taste receptors—the tiny cells that report the chemical makeup of external stimuli to the brain—in the testicles don't "taste" in the same way as the gustatory ones you use to determine if there's enough sugar in your tea. Research suggests that these "teste" receptors can sense bitter, sweet, and umami compounds and use that chemical input to control physiological processes or (literally) change direction. (Some users may experience a paywall.)

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.

Octopuses have taste receptors along their tentacles

Octopus suction cups are filled with modified sensory receptors that can bind with a greater variety of materials and transport a wider array of information, such as flavor, from tactile stimuli. These structures allow the animal to search for food as it crawls the ocean floor.

Chemicals from the gut have complex interactions with the rest of the body

Trillions of bacteria live in our guts, producing a wide range of molecules, hormones, and more. This review underscores the immune system’s pivotal role in the microbiota–gut–brain axis. Gut microbes influence immune cells and metabolites, which in turn modulate neurodevelopment, neural signaling, mood, and neuroinflammation—highlighting immune pathways as central mediators in gut‑brain communication.

Neural replays in mice help explain food aversions

Princeton University scientists published research in 2025 analyzing how mice learn to associate certain foods or flavors with feeling ill—even when there’s a time gap between eating something and feeling sick. The work, performed with grape Kool-Aid and injections of a substance that made mice sick, traced the literal “gut reaction” of how gut distress signals are linked to neural replays of what the mouse ate.

How texture affects taste

Texture is the brain's interpretation of several sensations, including pressure, as registered by our teeth, tongue, and finger tips, and sound, as recorded by our ears. Texture also speaks to food particle sizes—smaller than 35 microns contributes to the sensation of creamy—and the balance between flavor and mouth time, such as the crunch of a crispy chip or the bounce of a chewy caramel.

Over time, people develop a resistance to spicy foods

TRPV1 is a receptor in the body that detects potentially harmful things and responds in a variety of ways, including sweating, tearing up or a runny nose. Over time, more exposure to spicy foods can build up a resistance that minimizes these reactions.

The idea of a tongue map has been discredited (but taste sensitivity varies across the tongue)

The original tongue map, created by German researcher DP Hanig, recorded taste sensitivities reported in psychological studies. His findings were later translated and taken out of context, possibly giving rise to the faulty tongue map. In fact, taste receptors in the oral cavity respond to all tastes regardless of their location.

Tattoos remain visible thanks to immune cells called macrophages

Macrophages are a robust part of the human immune system. These large cells engulf invading particles, like viruses and bacteria, and use enzymes to break them apart. They perceive ink as a foreign body but can't digest them. Macrophages hold on to the ink, helping maintain the tattoo pattern.

Babies taste food in the womb via amniotic fluid, and it may influence future taste buds

Some estimates suggest that around Week 16 during pregnancy, a growing fetus can begin to taste amniotic fluid that contains flavors in the food that their mother consumed, due to taste bud formation. Scientists think those early flavor experiences may influence future taste preferences. Other scientific resources put that time much later, however—around Week 30.

Allergies occur when our immune system mistakenly considers a substance a threat

Immunoglobulin E antibodies, or IgE antibodies, may bind to an allergen, effectively labeling it as a threat. That triggers a cascade of actions in the body, including the release of histamine, which causes the characteristic itching and hives of allergies. Sometimes a cooked version of an allergen—like a cooked carrot—may look different enough from its raw form to the immune system that antibodies ignore it, and no allergic response takes place.

Tattoos remain visible on your skin thanks to immune cells called macrophages

Receptors on the cell surface are key to whether a virus is successful

Viral receptors are key regulators of host range, tissue tropism, and viral pathogenesis—basically, the door locks on cells allowing viruses to invade, if they have the right key. How this process works at the microscopic level determines whether a virus is able to trigger a widespread illness in the host.

Hookworm infection, though risky, may help fight certain health conditions

Early clinical trial research suggests that the parasites trigger the production of specific proteins that quiet our immune systems. This keeps the parasites from being killed, but it also quiets the inflammatory response that underpins allergies, type 2 diabetes, celiac disease, and other autoimmune conditions. Researchers still caution that infection with too many hookworms can cause serious medical complications and that this is not a standardized or approved medical treatment.

Fevers are an immune response to create hurdles for pathogens

Substances called pyrogens prompt the brain to raise the body temperature to levels where bacteria and viruses struggle to survive. The higher temps also support immune cells fighting off the invaders.

Mycotoxins are toxic compounds produced by fungi—some show up in food

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.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

We may be using Q-tips in our ears—even when we shouldn't—because they can stimulate pleasure nerves

People continue to use Q-tips inside their ears even though we know it's risky. Some clinicians suggest that beyond the desire to get water out, this may be because the nerve bundle called the vagus nerve, which spans from the brain to the large intestine, can be stimulated that way, causing a pleasurable sensation in other body parts including the heart, belly, or genitals.

The inner life of a cell

White blood cells are responsible for protecting the human body from infection. This video uses biophysical data from Harvard researchers to accurately demonstrate what goes on inside one white blood cell as it works within the immune system.

Teaching immune cells to fight cancer

CAR T-cell therapy is a type of immunotherapy, which involves strengthening the immune system to attack cancer cells. Patient T cells, which manage immune responses and are responsible for killing pathogen-infected cells, are collected and re-engineered to produce surface-level proteins called chimeric antigen receptors. These CARs, now able to bind to specific proteins on cancer cell surfaces, are multiplied into the millions and infused back into the patient.

Adhesion molecules and intercellular junctions allow cells to connect together

While some organic structures are mostly composed of non-cellular components (e.g., collagen and calcium phosphate minerals in bones), tissues and organs composed of connected cells rely on specialized proteins and connections to create watertight seals that protect cells within the interior from environmental molecules.

How the body produces its own opioids

Opioids act on the body's own opioid receptor system. The endogenous opioid system comprises four molecule receptor types found throughout the body. When activated, these receptor types trigger the release of dopamine and suppression of noradrenaline, neurotransmitters, respectively, associated with reward and alertness. This opioid system helps regulate emotions, and its disruption is linked to neuropsychiatric conditions, including depression, PTSD, and Alzheimer's disease.

Turtles' sense of direction comes from sensitivity to Earth's magnetic field and wave movement

Female sea turtles use this ability to migrate hundreds of kilometers across the ocean from their feeding grounds to the beaches where they were born to lay their eggs. Researchers have found that these turtles can reach these beaches despite ending up significantly off course as they detour away from predators or toward foraging territories.

How does food move through the body?

Food passes through the digestive system via muscle movement known as peristalsis, during which a rippling contraction slowly pushes content through tubular organs, such as the esophagus and intestines. This is similar to what happens when one squeezes a tube of toothpaste, contracting the tube behind the content and forcing the tube in front of the content to expand, allowing the content to move forward.

Twin studies suggest celiac disease is among the more genetically-linked disorders

Genetics appear to play a larger part in this condition's development than many other autoimmune disorders. Research shows a roughly 60-75% genetic probability that if one identical twin has it, the other will too. Celiac triggers a small intestine attack when people eat gluten, a protein commonly found in wheat, barley, and rye.

Watch what the Ebola virus does inside our cells and organs in order to spread and survive.

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.

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.

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

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

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.

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

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

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

The use of fungi to detoxify land and water—a process known as mycoremediation—has been used to clean up natural resources affected by the 2025 California wildfires.

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

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.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

Recent research found that the brain doesn't seem to massively rewire following amputation—upending earlier beliefs about the cause of phantom limb pain.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

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.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

Iran's Revolutionary Guard Corps is independent of Iran's regular army and is one of the most powerful and influential military-political organizations in the Middle East.