A macrophage can eat 100 bacteria, on average, before it's exhausted

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.

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

There are between 10 and 100 trillion bacteria in the gut

The composition of our microbiome is essential to overall health. Anything that disrupts the balance of the trillions of bacteria may be harmful—even treatments meant to fight infection, like antibiotics.

Chronic inflammation can cause cellular damage and could lead to cancer

Over time, this cellular defense system can inadvertently damage cells and tissues when it's in this heightened alarm mode over a prolonged period. This occurs because, when immune cells are sent somewhere without a true target, they may attack healthy cells and tissues.

Measles attacks the body’s immune system, leaving it vulnerable to secondary complications

A measles infection begins in the lungs, where it hijacks cells known as macrophages and begins to replicate itself. It then uses a Trojan horse method to enter the lymph nodes, where it attacks vulnerable T and B cells. Symptoms include fever and rashes.

Some mosquitoes are key pollinators—and eat disease-carrying mosquitoes

​​There are more than 3,500 species of mosquitoes, and only a small fraction of them bite humans. They also play vital roles in the ecosystem: One young elephant mosquito, for example, can eat dozens of smaller mosquitoes that bite humans in just one day. Sometimes mosquito-gobbling species are released by humans to control other mosquitoes.

We're breathing microplastics

White blood cells can't fight off microplastics and that sparks inflammation and bigger health risks. They're in our food, water, even the rain. What does that mean for us?

Microbes are essential to creating the many varieties of cheese, influencing texture and taste

Microbes break down proteins and fats and produce compounds with distinct tastes. These microbes can include bacteria (like the one used to give Swiss its trademark holes), molds (like the ones that give blue cheese its distinctive veining), and countless other tiny organisms.

Most cells undergo programmed, controlled death

In the average adult human, apoptosis occurs in 50 billion to 70 billion cells daily when proteins managing a cell's life cycle send signals that the cell is damaged, causing it to break apart into smaller pieces that are consumed by white blood cells. The consumption prevents damage from spreading via cell division.

A quick video on how your immune system works

Explore how your immune system’s vast network of cells, tissues, and organs coordinate your body’s defenses against bacteria, viruses and toxins with this 5-minute TED talk video.

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.

CRISPR-Cas systems act as genetic memory banks for defending bacterial cells

When viruses called phages inject DNA into bacteria, some bacterial species store bits of this DNA in their own genomes. This allows them to recognize and destroy the same virus if it attacks again.

There's no definitive test for inflammation, or a baseline for what's considered normal

Existing tests can pick up proteins that indicate an immune response—in particular C-reactive protein, which the liver produces when the body's stressed—but that won't tell you why there's inflammation nor if it's chronic or acute inflammation. (Some users may experience a paywall.)

Women typically have more robust immune responses than men

This difference helps women better combat infectious diseases, but this more turbo-charged response may also make women more vulnerable to autoimmune diseases by potentially priming their immune systems to overreact to their own cells and tissues and label them as invaders that must be destroyed. Roughly 80% of American women have autoimmune conditions.

The adaptations of metallophiles and how they can be harnessed for bioremediation

These extremophiles have adapted to biomes with very high concentrations of metals and toxic chemicals by developing mechanisms to isolate these substances within cellular compartments and break them down into less harmful forms with specialized proteins. They have the potential to support the decontamination of metal-rich wastewater and soil, as well as the extraction of rare-earth metals.

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

'Buffy coats': The 1% of blood that helps fight off disease

When blood is centrifuged, white blood cells and platelets form a layer called the buffy coat between the plasma and red blood cells. This layer makes up less than 1% of blood, but its heightened leukocyte concentration makes it useful for toxicology research.

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

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

How humans digest food

Every day, the average human eats close to six pounds of food—all of which must be processed by the digestive system. Ten organs collaborate to transform food that the mouth chews into the energy needed to stay alive. (Stretched out, these organs...

Taste buds have evolved to fill a wide variety of functions

Taste buds do more than let you experience your favorite food. These peripheral organs can sense the chemical makeup, potential toxicity, and fleeting experience of flavor, giving the body a chance to respond to undesirable chemicals or tell the brain that you should reach for another scoop.

How metabolism, when cells convert molecules into energy, works

Metabolism is when a cell’s internal network of chemical reactions breaks down food molecules and transforms them into pieces of the cell itself. Sometimes, cells build replacements for worn-out parts. Other times, they build energy molecules that power the cell’s activities.

Drug-resistant staph infection is one of the deadliest superbugs

Methicillin-resistant Staphylococcus aureus (MRSA)—the superbug version of staph infection—is responsible for more deaths than any other superbug, killing more than 120,000 people globally each year. The bug is leading cause of hospital infections, and is harmless on the skin but causes severe symptoms once inside the body.

Learn how monoclonal antibodies, which mimic the body's antibodies, can fight diseases like Ebola

Monoclonal Antibodies mimic the antibodies produced naturally by the immune system. These molecules target specific parts of the virus, preventing them from entering cells or interfering with their ability to cause harm or infection.

Lengthy incubation periods are why it’s tough to link foodborne illness to specific foods

People may not get sick from a foodborne pathogen for several days after consuming it, making it a challenge to link the illness and its cause. Factors influencing when a person starts feeling sick—even as the pathogen is multiplying in the gut—include individual variations in immune systems and gut microbiomes, what other foods are in the person’s body, and how much of the pathogen was consumed.

The marvels of mucus

Mucus—otherwise known as snot or phlegm—has a gross reputation, but the substance is actually of vital importance, lining the moist surfaces of our nose, intestines, lungs, and more. It plays a constant role in keeping our tissues from drying out and acts as a line of defense, but if it gets too sticky or thick, it can cause problems. Read about the marvels of mucus here.

Myokines are molecules that facilitate some of the benefits of exercise

When muscles contract, they release ‘hope molecules’ (myokines) such as IL-6 and irisin. These proteins then travel through the bloodstream to reduce inflammation, improve insulin sensitivity, and even support brain repair. This piece illustrates how movement triggers a systemic healing cascade throughout the human body.

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

The second phase of acute stress: the 'slow' response

The body's reaction to acute stress involves two responses: fast and slow. The first occurs immediately, with the central nervous system triggering the release of adrenaline. The second releases cortisol, which elevates blood sugar and blood pressure and restricts nonessential functions like digestion and the immune system.

How snake biology allows them to eat prey larger than they are

Possessing flexible skulls with elastic ligaments and unfused jaw bones, snakes can open their mouths to engulf much larger prey, and adjustable airways enable them to continue breathing while their teeth grip onto their food. Through slow digestion and specialized cells that decompose bones, some snakes can survive on a single large meal for over a year.

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

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.

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

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.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

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.

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.

About 12.5% of US adults experience a phobia in their lifetime, a diagnosis that hinges on the intense fear interfering with daily life and persisting for at least six months.

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.

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.

See images of medical cases of firework injuries shared on this 'Instagram for doctors.' (Warning: Graphic content)

The Nasdaq's 'Magnificent 7' companies are responsible for roughly 40% of the Nasdaq 100 index's gains, while the remaining 93 companies account for the other 60%.

See how Budweiser's famous Clydesdales spend their days at Warm Springs Ranch, where roughly 70 to 80 of the beer brand's giant horses can be found at any given time.

Calculate how much of your tax dollars go to each federal program based on your income, filing status, and number of children

Massive 3D printers have been used to build homes by stacking layers of 'concrete toothpaste,' a fire-resistant material that effectively insulates against outside noise.

See photos of Meteora, a mountainous site in central Greece, home to 14th-century monasteries perched atop soaring outcroppings.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.