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

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.

Pediatricians look for a list of behaviors to signal typical hearing development

These markers of typical hearing development among infants and toddlers include turning head to sound sources within the first five months of life, babbling by about 11 months, and trying to imitate simple words by 17 months of age.

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...

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.

Infants are particularly at-risk for ear infections

The Eustachian tubes, which connect the middle ear to the upper throat and help to drain fluids and equalize pressure, are relatively flat at birth, making it hard for gravity to assist with drainage. The angle of these tubes changes and becomes steeper as we age, making fluid buildup in the ear canal less common.

Newborns have a strong sense of smell

Babies are drawn to their mother's smell—and the particular odor of their mother's breast milk—within days, even as their vision remains blurry for months after birth. In the womb, the olfactory center also forms in the early stages of development.

Exposing fetuses to certain flavors in the womb could lead to children being less picky eaters

A new study found that 3-year-olds were less averse to the smell of vegetables they had been repeatedly exposed to in utero, suggesting that what mothers eat in late pregnancy can leave a lasting imprint on their children's tastes.

Neanderthals commonly had surfer's ear, a potential sign of extensive seafood collection

Analysis from 2019 found that about half of the 23 Neanderthal skulls scientists examined seemed to have the bony growths in the inner ear, signifying they had surfer's ear. Those growths suggest our ancient relatives, dating back to between perhaps 100,000 and 40,000 years ago, were potentially hunting fish, mollusks, or other marine resources in chilly waters.

Babies don't develop a circadian rhythm right away

Newborns don't develop circadian rhythm until they are a few months old, which helps to explain their erratic sleep schedules. When they're around three months old they begin to release melatonin, which influences sleep, and around the same time they develop more regular sleeping routines.

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.

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

This temporary organ, formed from maternal and embryonic tissue, ultimately attaches to a fetus via the umbilical cord. It transports nutrients, oxygen, antibodies, and more from the mother to the developing fetus. It also carries carbon dioxide and waste away from the fetus. The placenta—which forms only during pregnancy—is expelled during childbirth, or it needs to be removed to prevent toxic maternal infections and extreme blood loss.

Cochlear implants stimulate nerves inside the ear to provide the sensation of sound

In a surgical procedure, one part of the implant is placed under the skin behind the ear and electrodes are threaded into the cochlea in the inner ear. Another part of the implant sits behind the ear and picks up sound and then converts it into patterns of nerve stimulation.

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.

Tornadoes produce inaudible signals to humans hours before forming

Researchers at the National Oceanic and Atmospheric Administration have found that tornado-producing storms generate specific sounds below the range of human hearing, much like the infrasonic signals produced by earthquakes and avalanches. Although difficult to distinguish from wind noise, scientists hope to build systems that use these signals to improve tornado forecasting.

Some animals may speak because of duplicated connections in the brain

Neuroscience suggests that connections responsible for motion made during embryonic brain development—such as those connecting hearing and movement pathways that allow reactive motion when started—are duplicated and connected to the larynx in some animals. This allows some mammals and song-learning birds to speak, provided they have the necessary physiological structures.

Ultrasound machines emit and collect high-frequency sound waves to construct images

Before its use in medical imaging, the technology was employed in World War I for submarine detection, the same way bats use sound for echolocation of obstacles. Differences in the penetrating power of different frequencies allow medical professionals to detect different structures in the body.

Listen to the earliest known recording of a whale song

A recording of a humpback whale was taken by scientists from the Woods Hole Oceanographic Institution near Bermuda in 1949, but forgotten for decades. When first captured, researchers didn't know what animal they were hearing, and therefore didn't catalogue the recording. The well-preserved audio was found by the team's archivist in 2025.

See this graphic describing what different decibel levels mean for hearing loss

From the sound of a ticking watch, which is roughly 20 decibels, to the sound of a gunshot at 140 decibels, the Hearing Health Foundation breaks down the decibels of daily sounds in this chart, noting that sounds louder than 70 decibels are considered harmful.

Each day, about 60 US pregnancies end in stillbirth

This online memorial for families who experienced the unexpected death of a fetus 20 weeks or older is the result of ProPublica reporters inviting 60 families to share their baby's name and answer some questions about their unfulfilled wishes for their children. About 21,000 babies are stillborn in the US annually. About the same number of children die in the US during their first year of life.

‘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.

Tinnitus is derived from the Latin verb tinnire, meaning to ring

Read the entry in The Physical Dictionary by Stephen Blankaart, from 1693, where the word first appeared in English.

Emotional crying is an important and cathartic process

Though babies don't initially produce tears when they cry, this podcast discusses how humans are hardwired to cry throughout life. Most crying research relies on self-reporting of crying and emotions. This podcast notes that there aren't neuroimaging studies of crying—they're quite expensive to complete. As a result, the brain precursors and processes during a bout of crying remain understudied.

Your brain appears to age in five distinct stages

Analysis of brain scans from about 4,000 people has helped scientists identify five major stages of our brain's maturation from birth to death. The pattern of connections inside our brains seem to shift, on average, at ages 9, 32, 66 and 83. (Some readers may experience a paywall.)

Nasal congestion is a common side effect of pregnancy, called pregnancy rhinitis

In one recent study, almost 100% of pregnant women experienced this condition in their third trimester. The congestion is likely due to hormonal changes and neurophysiological factors, and it may also worsen at night due to circadian factors and gravitational redistribution when lying down. Treatments include saline nasal irrigation and the use of nasal strips to widen the nasal valve area.

Early texts claim Jesus was conceived on the same date of his death

Though celebrations of Jesus’ birth weren’t formalized for several hundred years after he lived, it was more common to commemorate his death. Some early Church writers connected the presumed date of his death—March 25—with his conception, implying a birth date of Dec. 25.

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.

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.

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

Fish populations in the Great Barrier Reef have increased after installing waterproof speakers on the ocean floor that played recordings of sounds from healthy coral reefs.

A pickleball's loud 'pop' sound can reach 120 decibels, which is equivalent to a hammer hitting a nail

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

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

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

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

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

'Silent' fireworks have gained more interest in recent years as a quieter celebratory option.

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

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.

Trace how the Bill of Rights, inspired by centuries of political theory, took shape between 1774 and 1789.

Learn how to read a prospectus, the juicy document that any company must file with the SEC before going public.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Abraham Lincoln was almost assassinated weeks before his inauguration as he traveled from Illinois to DC through Baltimore in 1861; it took two independent claims for Lincoln to be convinced the threat was real

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

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.

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak each year.

The Beatles' US label rejected the band's first two singles, 'Please Please Me' and 'From Me to You,' with one executive calling the band 'dead in the water.'

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.

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

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.