What does a beating human heart look like?

Explore the heart in this interactive 3D model

The heart is the fleshy muscle at the heart (pun intended) of the circulatory system. The heart is segmented into four chambers: two for intake (the right side) and two for output (the left side). Controlled via the autonomic nervous system, also known as the involuntary nervous system, the heart typically beats 60 to 100 times per minute, sending nutrient- and oxygen-rich blood throughout the body.

Ten things to know about your heart

Your heart does amazing things day in and day out. Its main job is crucial: It keeps oxygenated blood circulating throughout your body. Did you know that, other than your cornea, every cell in your body gets blood from your heart? You may not think...

Blood leaves the heart at speeds around 12-16 miles per hour

Blood is pumped around the body through the circulatory system, aka the cardiovascular system. This system comprises the heart, arteries, veins, and capillaries. This video is the first in a multi-part series on the circulatory system, focusing on the role of the heart, the pump that powers the entire system.

How the heart achieves its first beat

Scientists observed zebrafish embryos as they grew and isolated the several-second-long initial heartbeats to better understand this crucial moment in every heart's life. The zebrafish's heart starts beating 20 hours into their existence. Each heart cell activates electrically at random, without rhythm. As these cells mature, they become more sensitive to electrical charges; as they all fire, a rhythm is established and a pulse is born.

How heart transplants work

Heart transplants require an old heart to be removed and a new one to be installed without killing the patient. How does that work? In this easy-to-understand five-minute video, learn each step of the intricate process, from donor matching to the preservative solution a heart is doused in while it is transported.

Explore the abundance of different types of cells in the human body

Lacking a nucleus and other organelles to maximize space for oxygen-carrying hemoglobin and enhance maneuverability through narrow capillaries, there are about four times as many red blood cells and platelets as all other cell types in the body combined. However, about half of the body's cell biomass consists of skeletal myocytes, or muscle fibers.

Explore human anatomy with these beautiful images

The Human Organ Atlas offers detailed 3D images of dozens of human organs. It was created with very bright X-rays from a particle accelerator, which is formally called a synchroton imaging method.

Muscular system explained

Skeletal, cardiac, and smooth muscles form the system that powers movement, survival, and daily life. Skeletal muscles are voluntary, enabling conscious actions like lifting or walking, while cardiac and smooth muscles are involuntary, controlled by the autonomic nervous system. From every heartbeat to each breath, these three muscle types work in harmony to keep you moving, thriving, and alive.

Low cell division rates in heart cells make heart cancer particularly rare

The heart's location in the chest also offers protection from external cancer-causing factors. The disease affects about 3 in every 10,000 people, though most cases arise from metastasis from other body parts.

This is what happens inside your body when you're sick

This video details the biology of what happens inside the human body during illness.

A beginner’s guide to the brain

Small but powerful, the brain constitutes only about 2 percent of the human body. However, it runs jus about everything, day and night, all year round. Learn about the different parts of the human brain, as well as its unique defenses, like the blood brain barrier in this four-minute video.

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

This NPR video makes clear that there are surprising similarities between how our bodies and fireworks function. Fireworks and our bodies are both packed with carbon atoms, and have controlled releases of energy that create heat—keeping the human body warm or fueling fireworks' heat, respectively. What's more, the human body even emits a tiny bit of light somewhat similar to fireworks—though it's not visible to the human eye.

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

Pulsatile tinnitus is when you hear thumping synchronized with your heartbeat

This rare type of tinnitus, which sounds like rhythmic thumping or whooshing, is often linked to blood vessel conditions or high blood pressure. Lowering blood pressure through exercise and food choices can help reduce the severity of this condition.

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.

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

The body's response to cardiac arrest has been linked to near-death experiences

Most people who report near‑death experiences experience events like out‑of‑body sensations, altered cognition, emotional and spiritual shifts, or even supernatural phenomena, particularly during cardiac arrest. Research suggests many such experiences may be linked to brain-generated sensory distortions that can be experimentally replicated, suggesting a physiological rather than mystical cause.

What is it like to be a bee?

Scientists have long known the intimate features of bee anatomy: six limbs, five eyes, lots of hair, a long, tasteless tube -like tongue, and wings that stroke close to 12,000 times a minute. But getting inside the mind or consciousness of a...

Earth's inner structure is a dynamic system of layers in constant, slow motion

From the crust to the core, each of Earth's layers—some solid, some liquid—plays a role in generating its magnetic field, moving tectonic plates, and cycling matter. These details are determined through modeling since humans have only drilled 12 kilometers underground.

Key components of a joint: bones, cartilage, ligaments, tendons, and fluid

A human joint is any place in the human body where two bones connect. This junction allows for movement, but is prone to breakdown and pain. This nine-minute video explains normal joint anatomy and function, with particular attention to the different types of motion each joint facilitates.

Theoretically, you could lose a bunch of your organs and still survive

If surgeons removed organs including one of your lungs, a kidney, your spleen, appendix, tonsils, part of your liver, and even some of your reproductive organs you could still survive. Watch this animated video which dives into the organs you could conceivably live without.

Watch a video that visualizes what really happens inside a credit card network when you make a purchase.

Every tap sets off a lightning-fast relay. When someone buys coffee with their Visa, a tiny "runner" races between the coffee shop's bank, Visa's network, and their bank—all in under a second. The catch? No money has actually moved yet. Here's what really happens behind that instant "Approved."

Every organ in a mother's body changes during pregnancy

There's limited real estate inside a mother's body; as the uterus grows both up and out, it shifts other organs to make space. A pregnant woman's body produces hormones to loosen muscles to allow for this expansion. Pregnancy also triggers other changes, including faster breathing to compensate for decreased diaphragm range.

The pancreas releases digestive enzymes and regulates blood sugar

The pancreas weighs about the same as a deck of cards and is smaller than the average adult human hand. This lopsided glandular organ controls blood sugar levels through insulin production and helps the body digest food by creating a neutralizing tonic filled with digestive enzymes.

Visualizing a stroke at the microscopic level

By far the most common type of stroke is what is known as an ischemic stroke. This occurs due to either an embolus (a blood clot that travels to the brain from elsewhere in the body) or a thrombus (a blockage that forms within the brain itself).

Why don't giraffes get hypertension?

The average blood pressure of a giraffe is about double that of a human, yet they don't suffer from the symptoms of high blood pressure that humans do: stiffening of the left heart ventricle, shortness of breath, fatigue, or swollen legs and ankles. This article explains how giraffes have evolved to have the "biological equivalent of support stockings."

Tattoos, explained

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.

Explore the animals that populate the depths of the ocean, from fish and coral in the first few hundred feet, all the way down to the bottom of the Mariana Trench.

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.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

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

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.

This site reaches millions of visitors who are tired of AI chatbots and seeking human connection. Pretend to be an AI chatbot and ask questions, provide answers, and draw for people in real time.

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

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

How Amazon operates a 'flywheel' business model, a self-reinforcing cycle that drives continuous growth

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

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.

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

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Hear 50 years of iconic hip-hop samples, the genre's foundational looped tracks

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.

Against his wishes, Albert Einstein's brain was removed before his cremation, and the pathologist responsible stored it for decades in mason jars within a beer cooler.

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.

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.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'