Examine this captivating animation 'building' a human—illustrating the roughly 42 weeks of fetal development.

Explore this week-by-week visualization of pregnancy

This graphic illustrates how development proceeds during each week of pregnancy, tracking what shifts and milestones typically occur during each stage of the process. It also includes typical weights of the fetus throughout.

Fetal development, week by week

Gestation is the period of time between conception and birth when a baby grows inside the mother's womb. Changes occur constantly over the course of these 40 weeks. At week 17, for instance, the skeleton of a fetus begins changing from soft...

The human body in 3D

Zygote Body is a free human anatomy tool that allows users to explore the intricacies of the human body in stunning detail. With the click of a mouse, users can isolate by body system or view anatomical structures from any angle. Check out this...

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.

How women grow tiny humans inside of them

Pregnancy is a complex biological journey, lasting about 40 weeks. When a sperm fertilizes an egg, that event triggers intricate cellular and hormonal processes, driven by hardwired cellular instructions, which lead to cell division, differentiation, and development—ultimately culminating in the birth of a baby.

View an illustrative journey of sperm cells navigating toward fertilization

In this series of comic-style panels, a "fellowship" of sperm cells travels through fictionalized versions of reproductive anatomy on their way to an egg cell. Each panel includes informative commentary on each step of the adventure, with research insights provided by a reproductive biologist, a biomedical scientist, and an andrologist.

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.

Explore this interactive visualization of the IVF journey as a parent or child

This step-by-step graphic takes the viewer through different challenges and stages of the IVF journey, from a parent's and a child's perspective, including a parent's struggle when other families become pregnant around them, even as IVF is not working for their family.

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.

'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.

Using artificial wombs to improve preterm infant health outcomes

Researchers at a hospital in the US have successfully used artificial wombs to care for preterm lambs and are now looking at the possibility of human trials. This nine-minute video includes interviews with the researchers and explains the reasoning...

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.

Explore the human family tree

This interactive human family tree shows the various species that constitute the human evolutionary family. Click on each species or group image to learn more.

In the womb, a fetus may begin to hear at 18 weeks

Though little indentations form on the side of the fetus's neck at roughly nine weeks—with some formations taking place even before then—developmentally, these indentations don't become ears that allow a little one to hear until around 18 weeks.

Explore how the placenta acts as lungs, kidneys, and more in the womb.

The science and ethics of artificial wombs

Artificial wombs may be able to help preterm babies survive their early entry into the world and possibly curb the long-term adverse health effects associated with such premature birth. This article dives into the current ethics and science behind artificial wombs and ectogenesis, which is when a fetus develops in artificial conditions.

Artificial wombs and preterm births: an overview

Scientists are working to create artificial wombs that would help preterm babies survive their early entry into the world. But how much help could this technology provide, and how much of a problem are preterm births? This article details some of...

Touch is the first sense a fetus develops in the womb

During gestation, our sense of touch begins to develop around 8 weeks, starting with the development of sensory receptors in the face and, about a month later, in the palms and soles of the feet.

How the body produces urine

Things seem so simple when nature calls. But, how does the body actually produce the urine we so regularly and thoughtlessly expel? This detailed, comprehensive animation walks viewers through every step with precise illustrations, from the kidney's filters (known as nephrons) to the direct nerve connecting the bladder to the brain. See how the body does it here.

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.

Take a 360-degree look at biochemical activity from within a human cell

In this tour, users can observe the dynamic processes that occur within the basic units of the human body, including the production and transport of proteins and the assembly and disassembly of microtubules—thin, cylindrical structures that provide structural support and a means of moving material within the cell.

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.

Visualize a model of all of time, where our lives span less than the width of a human hair

The massive model was built across a Mojave Desert lake bed using 800 lights spaced just 10 meters apart. Within the model, the entirety of human civilization appears only in the final centimeter.

An animation illustrating the enormity of the universe

Look around you. Where are you? Where is this place you are occupying? Somewhere in a room, maybe in a city on a continent on a planet orbiting a star in a galaxy among billions. But… where is all of that?

Follow an IVF procedure from lab to transplant

What happens once eggs are harvested from an ovary? How does an embryo form within a petri dish? This detailed video offers a glimpse of the transformations eggs experience as women age, and how sperm are injected into eggs in some forms of IVF treatment.

In 1984, a dying infant lived for three weeks with a baboon heart

Pediatric-sized hearts are very hard to find. They're about the size of a walnut. When a premature baby girl was born with a fatal heart defect in 1984 her care team transplanted a 7-month-old baboon's heart into the patient. The organ was not genetically modified but still the infant lived for several weeks. This roughly hour-long documentary from the medical institution, features the patient's mother, clinician, and more discussing the controversial procedure and aftermath.

Data visualizations showing population growth around the world

This page presents data, charts, and analysis on changes in population growth around the world. Over the last few centuries, the human population has gone through an extraordinary change. In 1800, there were 1 billion people; today, there are more...

A gallery of medical illustrations from NIH

The National Institutes of Health provides educational materials for broad use. The institute hosts a Flickr account with many different image galleries, including this one (with over 70 images to date) that illustrate and annotate curious phenomena, from the life cycles of a malaria parasite to the comparison of male and female bladders. Explore the gallery here.

Exploring the link between history, art, and anatomy

Throughout centuries, art has played a vital role in sharing—and furthering—scientific understanding. This largely began in 1543 when physician Andreas Vesalius worked with an artist and engraver to transform learnings from his dissections into...

What does a beating human heart look like?

Tucked behind your rib cage and between your lungs sits your heart. This knot of cardiac muscle will (typically) beat billions of times throughout your lifetime, sending oxygenated and nutrient-rich blood throughout the body, powering countless biological processes that have enabled you to read this very paragraph. This two-minute video provides a glimpse of the mechanics happening inside your chest via an animated anatomical model.

Charting 4,000 years of human history

Care to hang all of human history on your wall? This data visualization charts 4,000 years of humanity. This "histomap" was originally published in 1931 and sold for $1 per copy of the 5-foot-long chart. It was said to detail the course of...

The history of ectogenesis and artificial wombs

While the science of artificial wombs is new, the idea goes back to a 1923 Heretics Society of the University of Cambridge lecture where an English biologist was one of the first people to propose an egg could be fertilized outside the womb. This...

The evolution of the human brain

The human brain, in all its staggering complexity, is the product of millions of years of evolution. Read on to find out about brain size and intelligence, language and brain development, and more.

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

Embryonic stem cells emerge around five days after fertilization, during the blastocyst stage of embryonic development. At this point, the embryo consists of about 100 to 150 cells and forms a hollow structure, and these cells are the ultimate source of all other cell types during fetal development.

Each part of the human body experiences aging differently

With global average life expectancy cresting at 73 years, understanding how the body ages is imperative to effective medical treatment and maintaining a desired quality of life. This 13-minute video dives into how the body and its organs age "from head to toe."

A step-by-step overview of the IVF process

In-vitro fertilization involves a sequence of complex steps to move from egg production to birth. This include stimulating egg production in the ovaries, egg harvesting and fertilization outside the body, embryo culturing and transfer, and methods to support in and increase the likelihood of full-term pregnancy.

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.

Watch this 2021 video demonstrating a full brain death examination

This video and accompanying article in the peer-reviewed New England Journal of Medicine show the then-standard steps of a full brain death examination—demonstrating the process on a medical dummy to search for pain, blinking, eye movement, cough, gagging, or other forms of responsiveness. (May need to sign up for a free account to view.)

Your brain appears to age in five distinct stages, with the pattern of connections inside your brain shifting, on average, around ages 9, 32, 66, and 83. (Paywall may apply.)