Embryonic stem cells can develop into any other cell type in the body

Stem cells become specialized cells through the activation or silencing of specific genes

After fertilization, when a sperm cell fuses with an egg, the resulting stem cell is described as totipotent—capable of transforming into any type of body cell or embryonic structures (e.g., placenta). Once differentiated into multipotent cells, they can only specialize further within specific cell type families, such as hematopoietic cells that become platelets and red and white blood cells.

There are three types of stem cells, each with different properties

Embryonic stem cells are "blank slates" that can change into any other type of cell. Adult stem cells can become specialized cells to replenish the supply or repair injury, while induced pluripotent cells are "reset" by scientists and used in clinical and medical applications.

Stem cells develop into a wide range of other specialized cells in the human body

Stem cells are different from other cells because they are capable of creating copies of themselves and producing other types of cells. For example, the ones found in our brains, bones, or muscles. Curious about stem cells? Here's a breakdown of how they work.

The difference between embryonic and adult stem cells

The main difference between embryonic and adult stem cells lies in their potential and origin. The former can become any cell type in the body, while the latter are limited to specific cell types. Embryonic stem cells also carry ethical concerns when used in medical or clinical applications.

In vitro gametogenesis: using induced stem cells to fertilize eggs

Using stem cells from skin and mouth cells could save hopeful parents time and money and spare egg donors from significant amounts of discomfort throughout the process. There are potential consequences, not just for infertility treatment, but for the ability to create customized cells of any type.

How to turn any cell of the body into a stem cell

Scientists have developed techniques allowing them to 'reprogram' any cell in the body into an induced pluripotent stem (iPS) cell, which can be used to create either more stem cells or specialized cells for use in experimental medical treatments. This page gives readers a brief introduction to the history of iPS cells, what researchers are studying with iPS cells, and challenges associated with iPS research.

Stem cells can reboot the ability of cells to repair themselves

Stem cells—special cells that can self-renew and evolve into new cell types—may provide a path to address aging. Instead of repairing aging cells, stem cells can replace a cell's "repair kit," effectively rebooting the internal processes of tissues to a more youthful state.

Bone marrow transplants were the first successful type of stem cell therapies

Bone marrow contains two types of stem cells: Skeletal (develop into bone, cartilage, and more) and hematopoietic, which create new blood cells. The latter are critical in bone marrow transplants, and give the recipient the ability to create healthy blood cells to fight diseases like leukemia.

'Artificial embryos': The hidden steps in forming a spine

Somitogenesis is the process by which segmented body structures like vertebrae form in embryos. While the process is well understood in animals like mice or zebrafish it is difficult to study in humans. But now, researchers have created a model of somitogenesis, using pluripotent stem cells, called an axioloid.

What happens during the first eight weeks of pregnancy?

The first weeks of embryonic development, known as embryogenesis, are one of the most critical phases during pregnancy. This simple breakdown from the Khan Academy illustrates what we know about how the complex process unfolds.

‘Hope for Healing’: The first-ever use of an in utero stem cell treatment

In 2023, researchers at UC Davis performed the first-ever fetal stem cell transplant, attempting to cure a case of spinal bifida prior to childbirth using stem cells derived from the placenta. The trial, and others including an effort to treat muscular dystrophy, highlight the potential power of stem cell therapy.

Cells can last in the human body from days to a person's entire life

Despite claims that a person's body replaces itself every seven to 10 years, the rate at which cells die and are replaced varies by cell type. Gastrointestinal cells that line the digestive tract and stomach last only a few days, while some heart muscle cells and most neurons are around from birth until death.

Only about 0.0001% of sperm, on average, successfully reach the uterine cavity

We've evolved to make pregnancy a complex and difficult process. From the initial development of the blastocyst, to the energy and nutrients needed to grow a new human, our bodies are both fighting and supporting fetal development.

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.

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.

Cells create more organelles and duplicate their genetic material before dividing

As part of the cell cycle, this ensures that after mitosis—the process of cell division—the two resulting daughter cells possess the tools necessary to complete the functions of their parent cell, including accumulating energy and making proteins. During meiosis, four egg or sperm cells are created, each with half the parent cell's DNA.

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

'Cells Making Cells': 'Science Sam' discusses the potential of stem cells

In this episode of the Ologies podcast, host Alie Ward picks the brain of science communicator Samantha Yammine—whose PhD work focused on neural stem cells. The conversation covers everything from the earliest days of stem cell research to what the future of stem cell therapies may look like.

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.

Watch a salamander grow from fertilization to hatching

New microscopy techniques have allowed scientists to image the development of animal embryos with unprecedented detail. This six-minute time-lapse reveals the development of a salamander from initial fertilization to hatching from an egg.

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

Organoids: 3D organs grown from stem cells in the lab

An organoid is a three-dimensional construct composed of multiple cell types that originate from stem cells that can simulate the architecture and functionality of native organs. One big benefit of these lab-grown organs is that drug candidates can be tested in model systems without needing live patients.

Women are born with all the eggs they will ever produce in their lifetime

Girls are born with an estimated 1 million to 2 million eggs in their bodies, but around 10,000 die monthly before puberty. Scientists have not yet figured out why there's such an excessive number of eggs prior to menstruation, but they've calculated that there are roughly 300,000 to 400,000 eggs left at puberty.

Fruit fly experiments helped identify genes responsible for major body development

The insects' fast life cycle and affordability have allowed geneticists to quickly identify which genes are responsible for limbs, eyes, and other body structures by inducing mutations. The same genes may be responsible for different parts of a species' body, such as limb-building genes being responsible for wing pigmentation in butterflies.

Genetic analysis indicates that every organism on Earth evolved from a single cell

LUCA—the last universal common ancestor—lived about 4.2 billion years ago and likely obtained energy through the conversion of carbon dioxide and hydrogen gas consumed from atmospheric gases at the ocean's surface or hydrothermal vents—openings on the seafloor where fluid warmed and enriched with minerals by Earth's interior is expelled.

Some organisms are composed of a single cell visible to the naked eye

By incorporating tough, cellulose-rich cell walls, rapid movement of molecules via cytoplasmic streaming, and other biological techniques, some unicellular organisms can bypass the physical limitations that restrict the size of cells. Organisms such as the Stentor coeruleus and Acetabularia can be seen without microscopes.

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.

Ordinary bee larvae can develop into queen bees upon being fed royal jelly

Royal jelly is a protein-rich, yellowish substance produced by worker bees in a honeybee hive. After three days, only a few continue receiving the jelly, which triggers the development of ovaries and other traits not found in workers. The first candidate to emerge becomes queen.

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

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

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.

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

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

About 2,000 US babies are born annually without some portion of their limbs, potentially leading to a lifetime of pricey prosthetics.

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.

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.

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.

An Ebola vaccine was developed during the 2018 west African Ebola outbreak, but the 2026 Ebola outbreak is with a different species of the virus, not the one that the vaccine is approved to treat.

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.

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

SpaceX's S-1 or 'prospectus' revealed many previously unknown details about the company, including its unprofitability despite doing $18.7B in revenue in 2025, exactly how many voting shares Elon Musk will have in the company (roughly 85%), and more.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

Salvador Dalí believed he was his own dead brother, who had died nine months before he was born

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

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.

Learn more about the history of fireworks, which dates back to an accidental invention during an alchemist's quest for information about immortality.

One disco producer saw 'Star Wars' four times on its opening weekend and was so inspired that he recorded the album 'Star Wars and Other Intergalactic Funk,' which produced a chart-topping single.