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A sequel to one of the most popular NOVAs of all time, "Miracle of Life," this Emmy Award-winning program tracks human development from embryo to newborn using the extraordinary microimagery of Swedish photographer Lennart Nilsson.

Trace human development from embryo to newborn through the stunning microimagery of photographer Lennart Nilsson.

Life's Greatest Miracle

US & Territories

(This program is no longer available for online streaming.) Water. Turn on the faucet and it’s always there. Without it we perish. But how safe is our tap water? In this special report narrated by Joe Morton, NOVA investigates what happened in Flint, Michigan, when local officials changed the city’s water source to save money, but overlooked a critical treatment process. As the water pipes corroded, lead leached into the system, exposing the community—including thousands of children—to dangerous levels of poison. NOVA uncovers the science behind this manmade disaster— from the intricacies of water chemistry to the biology of lead poisoning to the misuse of science itself. NOVA follows ordinary citizens and independent scientists who exposed the danger lurking in Flint’s water and confronted those who turned a blind eye. And discover the disturbing truth that reaches far beyond Flint—water systems across the country are similarly vulnerable. How can we protect ourselves from poisoned water? (Premiered May 31, 2017)

What exactly went wrong in Flint—and what does it mean for the rest of the country?

Poisoned Water

Whether they make you fat, fart, or freak out, microbes play a central role in your life. Right beneath your nose—on your face, in your gut, and everywhere in between—trillions of bacteria, viruses, and fungi are so abundant in your body, they outnumber your human cells. But these aren’t just nasty hitch-hikers. Many are crucial to your survival. Evidence suggests that a diverse microbiome can keep you healthy and, conversely, a damaged one could kill you. NOVA Wonders peers into this microscopic world to discover the fascinating, bizarre, and downright surprising secrets of the human microbiome, including the world’s largest stool bank, which transforms raw stool into life-saving poop pills.

Discover how a world of microbes living in and on you can make you sick-and keep you healthy.

What's Living in You?

Particles of Thought: Brain Guru

Your brain does all kinds of strange things. Neuroscientist Heather Berlin explains how it works.

How Algorithms Decide Who Gets a Kidney

Clinical algorithms are meant to guide doctors toward better care – but do they?
Algorithms are designed to make medicine more accurate. But when race is factored in, they can worsen inequality.
How Algorithms Decide Who Gets a KidneyPublished: September 9, 2025NARRATOR: For decisions like who should get a kidney transplant, doctors across many medical fields routinely use calculations that combine a patient’s medical history with additional data. These calculations are called “clinical algorithms.”MICHELLE MORSE, M.D. (Acting Commissioner, New York City Health Department): A clinical algorithm is a tool that clinicians would use to really best understand their patient’s specific diagnosis or treatment.NARRATOR: According to the clinical algorithm that Gregory’s doctors used, if Gregory had the same test results but was white, he would’ve immediately qualified for a kidney transplant evaluation. But why would race be a variable in determining kidney function?MICHELLE MORSE: There should be no reason why the physiological function of someone who’s Black would look different than the physiological function of someone who’s white.

Clinical algorithms are meant to guide doctors toward better care – but do they?

The Science of Scratch-Offs: What Your Brain Can’t Resist

You probably won’t win big playing the Lottery but your brain may want to keep trying.
Scratch-off tickets are big money for state-run lotteries. Is it the promise of winning big that keeps players in the game? Or is there something else happening in the brain?
The Science of Scratch-Offs: What Your Brain Can’t ResistPublished: July 7, 2025Alok Patel: Buy one of these, scratch off the foil and boom, you&#x27;re a winner, or more likely, a loser. But either way, instant lottery tickets, scratchers, scratchies, whatever you call them, are big money for lotteries, and behind it all is data, math and neuroscience. One of the most successful state-run lotteries in the country, the Massachusetts Lottery, made more than $4 billion in 2024 from scratch tickets. That&#x27;s a ton of money. That&#x27;s a ton of money. But Massachusetts uses the money for public services, such as road improvements and even schools. They bet on scratch tickets decades ago. In fact, the first scratch-offs were introduced in Massachusetts in 1974. Back then, they were pretty successful. Today, they&#x27;re outright huge. In 2024, scratch tickets made up almost two-thirds of all lottery sales. Now, part of this idea to bet big on scratch tickets came from an economist/Catholic priest.Richard McGowan: I had the interesting notion of being known as The Sin Priest, because I did my doctoral dissertation on the effect of excise taxes and anti-smoking laws on the cigarette industry, then I moved on to alcohol.Alok Patel: Richard McGowan was teaching a statistics course at Boston College in the early &#x27;90s when one of his students approached him.Richard McGowan: His father was the Massachusetts Lottery commissioner and he said, &quot;My father would like to talk to you.&quot;Alok Patel: The lottery was looking for ways to further develop scratch ticket games, so McGowan took the meeting.Richard McGowan: And he said, &quot;How do you think we could grow the instant games?&quot; And I said, &quot;Well, one thing you might be able to do is make sure people think that it&#x27;s a, quote-unquote, &#x27;fair game.&#x27;&quot;Alok Patel: McGowan and a group of students poured over ticket sales data from every state-run lottery in the country, and they thought the higher the payout for players, the more scratch-off tickets people would buy. But they had to figure out how to strike a balance between giving winners a good payout and making a profit for the lottery. So using statistical models, McGowan and his team created a system of recommendations for Massachusetts.Richard McGowan: The $1 tickets, we made a payout of around 90%, for the $2 tickets, I think we moved it up to 91% or 92%, and for the $5 tickets, the payouts were around 95%.Alok Patel: At the time, those payouts were higher than any state-run lottery, and they still are. Massachusetts still has the highest payouts across the country, according to a 2024 analysis. McGowan&#x27;s team also determined that the state should make more winning lottery tickets. They thought that the better the odds of winning, the more people would play, and their strategy worked, the Mass State Lottery is still one of the most successful lotteries in the country.But the lottery isn&#x27;t only popular in Massachusetts, playing the lottery is one of the most popular forms of gambling across the United States. I remember being a kid and seeing those numbers show up on the screen and being like, oh my gosh, I could buy a piece of paper and win $15 million? It&#x27;s ingrained into us as Americans to play the lottery.Speaker: Thanks for joining me. Stay tuned for This is America, Charlie Brown.Alok Patel: So is it only the promise of a fair game that keeps people playing? Maybe it&#x27;s the idea of beating the odds or the dream of winning big, or maybe there&#x27;s something else that&#x27;s happening in our brains that makes gambling so enticing. Your brain is hardwired to seek out rewards through a pathway fittingly known as the reward system. It links different brain regions involved with memory, motivation, pleasure and movement. Basically, your brain says, &quot;That was good, do it again.&quot; Scientists think this is part of why our species has been so successful, because the reward system reinforces behavior that once helped us survive. When you do something rewarding or something that keeps you alive, like eating, for example, neurons in your brain release powerful chemical messengers, such as dopamine, which causes you to feel a wave of satisfaction and encourages you to repeat that behavior again and again and again and again.But drugs, alcohol and gambling can hijack this process. Some researchers are finding that the anticipation of a reward sets off the reward center in the brain regardless of the potential outcome. Win or lose, doesn&#x27;t matter, I&#x27;m going to play anyway. And with excessive stimulation of the reward system, the brain becomes less responsive to the effects of dopamine, it builds up a kind of tolerance, so you need more of the stimulant to get the same effect, and this sets off a vicious cycle. Brain imaging studies have shown decreased activity in the decision-making part of your brain, the prefrontal cortex, in those with a gambling disorder. The overall effect of the constant stimulation of the reward system is that the behavior becomes more like a reflex than a choice.But what causes addictions is complex. Some researchers think that underlying factors, such as genetics or psychiatric conditions, influences who will develop issues with gambling. But unlike with drug or alcohol addictions, for those who excessively gamble, the promise of winning big, maybe even getting financial freedom, may seem like it&#x27;s right around the corner. But reality check, McGowan says those who play the lottery should always keep in mind the odds of winning stay the same no matter what you do.Richard McGowan: Every time you flip a coin, the coin doesn&#x27;t say, &quot;Oh, I was heads this time and I want to be tails the next time.&quot; Every time you flip it, the odds are exactly the same, and the same thing when you buy a lottery ticket, the odds of you winning are the same every time, thank you very much.Alok Patel: If you like this video, check out the Scratch &amp; Win podcast for the story of the unlikely rise of America&#x27;s most successful lottery. You can find Scratch &amp; Win wherever you get podcasts or on the GBH News YouTube channel. And if you or someone you know is struggling with gambling, help is out there, call the National Problem Gambling Helpline at 1-800-522-4700, that&#x27;s 1-800-GAMBLER, or text 800-GAM. Help is available 24/7 and is 100% confidential.

You probably won’t win big playing the Lottery but your brain may want to keep trying.

Critical Condition Outreach and Events

Explore the outreach toolkit, view upcoming screening events, and browse support materials for two NOVA films – Critical Condition: Health in Black America and When Machines Prescribe.
In <a href="https://www.pbs.org/wgbh/nova/video/critical-condition-health-in-black-america/">Critical Condition: Health in Black America</a>, Oscar-nominated and Emmy award-winning filmmaker Stanley Nelson investigates the dramatic health disparities in the US, even as scientists confirm that there are no meaningful genetic differences between races. From the deep history of pseudoscientific beliefs about race that still permeate modern medicine, to the latest research on how experiencing discrimination can directly damage the body’s DNA and biology, Critical Condition reveals the factors behind the health crisis facing Black Americans.The accompanying short documentary, <a href="https://www.pbs.org/wgbh/nova/video/when-machines-prescribe/">When Machines Prescribe</a>, produced by Llew Smith and Kelly Thomson, investigates the use of race in clinical algorithms. Designed to weigh factors like symptoms, medical history, and test results to achieve the best possible outcomes for patients, some common medical algorithms were built using data based on old pseudoscience about racial differences and their continued use has harmed the health of Black patients.<a href="https://www.pbs.org/wgbh/nova/video/critical-condition-health-in-black-america/">Critical Condition</a> and <a href="https://www.pbs.org/wgbh/nova/video/when-machines-prescribe/">When Machines Prescribe</a> are both available to stream on NOVA's website and the <a href="https://www.pbs.org/pbs-app/">PBS app</a>.
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<h3>Engage your community with the Critical Condition Outreach Toolkit</h3>We invite you to use the Critical Condition outreach toolkit to organize screenings and community discussions about racial health disparities, the factors that contribute to them, and the use of race in clinical algorithms. These events can be organized by any community organization to engage local medical professionals, scientists, medical institutions, public health officials, and others in conversations that explore racial health disparity causes, impacts, and solutions.<a href="https://drive.google.com/file/d/1h8EnAFTgmC1E_iECIQ1CpCxjnUqpO6Xf/view?usp=sharing">Critical Condition: Health in Black America - Outreach Toolkit</a>Interested in hosting an event about the documentary? Please complete the form below with details about the community event you would like to organize.<a href="https://docs.google.com/forms/d/e/1FAIpQLSewFQZQvpJLihbwpDxdbSxdTTD8Y7DNzSy-17noBR0rv0284w/viewform?usp=header">Submit community event information here!</a>
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<h3>Upcoming Events for Critical Condition and When Machines Prescribe</h3><ul><li>October 23, 2025</li><li>Critical Condition and When Machines Prescribe Screening and Panel Discussion</li><li>@ Charles R. Drew University, Los Angeles, CA</li><li>6 to 8:30 PM</li><li><a href="https://ticketbud.com/events/0c6fe32a-9e31-11f0-99d9-42010a7170c8">Register here!</a></li></ul><hr/><ul><li>October 28, 2025</li><li>Critical Condition: Health in Black America Screening and Panel Discussion</li><li>@ Ruth Williams Opera House, San Francisco, CA</li><li>6 to 8:30 PM</li><li><a href="https://ticketbud.com/events/c6a1b41e-8cf0-11f0-a168-42010a7170c7">Register here!</a></li></ul>
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US, US Territories, Canada

Critical Condition: Health in Black America

After centuries of pseudoscience, researchers examine the causes of racial health disparities.

What Happens to Your Body During a Speed Eating Competition?

Competitive eaters stretch their stomachs beyond limits. Here’s how they do it - and what happens inside their bodies.
Competitive eaters train to stretch their stomachs far beyond normal limits, allowing them to consume massive amounts of food in minutes. But this extreme practice takes a toll on the body. Here’s how they do it - and what happens inside their bodies.
What Happens to Your Body During a Speed Eating Competition?Published: January 8, 2025Alexis Zacharakos: What&#x27;s it like to eat 58 hot dogs in 10 minutes?Speaker 2: It is kind of fun. I think one time I gained like 25 pounds in 10 minutes. I don&#x27;t know if it&#x27;s fun, but it&#x27;s kind of insane to think about it.Alexis Zacharakos: So, what happens inside the bodies of competitive eaters as they tackle pounds of food in just minutes?Speaker 3: The stomach is a fascinating organ. It&#x27;s really two organs in one. The top part of the stomach is a receptacle, and the bottom part of the stomach is a grinder.Alexis Zacharakos: When food lands in the upper part of the stomach, the stomach naturally relaxes and expands. The pressure on the other organ sends a signal to the brain, &quot;I&#x27;m full and need to burp.&quot; This is your body&#x27;s signal that you should stop eating. Competitive eaters can dramatically relax and stretch their stomachs. That stretching allows them to eat more without feeling full, and they also train themselves to push past the feeling of fullness.Speaker 3: The speed eater just has a bigger capacity at complete relaxation, and then less of a stimulus to, &quot;I&#x27;m feeling full and I need to stop.&quot;Alexis Zacharakos: This is where the speed eater&#x27;s unique ability comes into play.Speaker 2: The way we look at the stomach, it&#x27;s just like a big muscle, and I think a resting stomach of an above-average eater can maybe hold three quarters of a gallon, or six to eight pounds, but we can hold sizably more than that.Alexis Zacharakos: The ability to expand the stomach is likely a combination of innate ability and dedicated training.Speaker 4: But it&#x27;s similar to somebody who might have a genetic tendency towards sprinting or towards marathoning. They have muscle fiber types that might lend themselves to either races that are intense and short and super-fast, or long and steady. However, you can&#x27;t get to the elite class of either kind of races without training.Speaker 2: So, the normal preparation for competitions is practice with the food, which sounds good, but it&#x27;s not great. And then you just drink a large amount of liquid to try to expand your stomach.Speaker 5: You have to always be trying to get a little bit more food in than you could in the past. That&#x27;s the only way to really grow.Alexis Zacharakos: Even with training and innate physiological advantages, the most seasoned speed eater will get tired during a competition.Speaker 5: You do a contest, it may only be eight minutes, it may only be 10 or 12. It doesn&#x27;t sound like a lot of time, but when you&#x27;re spending that entire time just shoveling food down at a really quick rate, it feels like a marathon.Speaker 2: It is really taxing on the body, and a lot of the times you&#x27;re just really pushing your body to the limit. And you end up sweating a lot, which is a little odd because you&#x27;re eating, but it is pretty physical.Alexis Zacharakos: So, what happens in the body when you put that much strain on it? Typically, as food moves into the lower part of the stomach, it mixes with gastric juices, and then gradually empties into the small intestine, a process that usually takes about four hours. But experts say that consuming larger quantities of food at a time may complicate digestion.Speaker 4: Undigested matter can stay in the gastrointestinal tract for days disrupting the gut microbiome. For example, there&#x27;s risk of small intestinal bacterial overgrowth, abdominal pain and diarrhea, and associated symptoms.Alexis Zacharakos: Consuming massive amounts of food in a short period can also cause it to sit in the esophagus as it waits to enter the top part of the stomach. The food piled up can cause vomiting or suffocation. It may also cause longer-term harm to the esophagus and the stomach.Speaker 3: If you get a tremendous expansion and rupture, you can actually rupture and tear the esophagus, which is called a Boerhaave syndrome, in which case all those contacts leak into the chest and become septic, and it can be really dangerous. In theory, I think you could potentially rupture the stomach if you just stretch it up far enough.Alexis Zacharakos: Research on how much the stomach and esophagus can stretch, and whether the stomach can fully return to its original size, is limited. Scientists are uncertain, but they&#x27;re concerned about permanent loss of stomach elasticity.Speaker 3: The stomach will relax and expand. And now the question is, can the stomach un-relax, and sort of get back to its normal size? Can those muscles get damaged so much that they don&#x27;t work properly?Alexis Zacharakos: If those muscles are permanently damaged, it could cause a disorder called gastroparesis. This essentially means the stomach muscles are paralyzed, leading to issues like poor digestion, bloating, and acid reflux. To counteract the short-term effects of speed eating, some competitive eaters may try to eat healthy foods, exercise regularly, or fast before and after competitions. Still, participating in training and events does often take a toll on metabolism, muscle health, and the body&#x27;s ability to recognize the feeling of fullness.Speaker 6: The day after a contest, because you have just had that giant stretch, is really hard to feel full after that with a normal meal. And so that part is a lot of training your brain to stop eating at a normal time, even though you have no sensation of fullness for the next week or so, because you&#x27;ve stretched that out, and it&#x27;s got to kind of bounce back to normal.Speaker 2: Through the years, my hunger and my metabolism has definitely slowed down, but I think it&#x27;s all been pretty relative.Alexis Zacharakos: Whether or not it takes a lasting toll, competitive eating is certainly extreme.Speaker 3: I don&#x27;t think it&#x27;s terribly unhealthy, but I don&#x27;t think it&#x27;s something that I personally would recommend. I&#x27;d play golf.

Competitive eaters stretch their stomachs beyond limits. Here’s how they do it - and what happens inside their bodies.

Why Hot Peppers Set Your Mouth on Fire

The chemical that makes chili peppers so hot evolved to keep animals from eating the plants, but humans have learned to like the sensation.
How does a chili pepper make your mouth feel like its on fire? When you eat peppers, capsaicin molecules fit into the heat pain receptors of your mouth, sending a false signal to your brain that&#x27;s identical to the one it would receive if you ate something literally burning hot.
Why Hot Peppers Set Your Mouth on FirePublished: December 20, 2024David Pogue: Here at the Berks Pepper Jam in Bethel, Pennsylvania.Speaker 2: Smell that. Mm!David Pogue: An annual festival of food, entertainment and contests, all centered on chili peppers.Woo! Bring it on!Speaker 3: We begin our contest with the long hots. Let&#x27;s turn up the heat. Eat!David Pogue: And we&#x27;re off.Zesty with just a hint of poison.Speaker 3: Round two. We&#x27;re going to start with the Red Fresno pepper.Eat! Eat! Eat! Eat! Eat! Eat! Eat! Eat!David Pogue: Got to be some easier way to learn about molecules.Speaker 3: All right. Are we ready? Eat!David Pogue: That was not designed for human consumption.Speaker 3: Round number four, habanero peppers.Eat! Eat! Eat!David Pogue: It hurts my body. I didn&#x27;t know I had are on fire.Speaker 3: 10 more seconds. You got this.David Pogue: I can&#x27;t.Speaker 3: No! No! Don&#x27;t do it! No!The Orange Copenhagen pepper. Eat!David Pogue: What am I doing? Oh, man. Oh my god.Speaker 3: Don&#x27;t do it!David Pogue: I want it.Cheers!Speaker 3: No!David Pogue: So I&#x27;m the first to fall. How does a pepper&#x27;s capsaicin convince my mouth it&#x27;s on fire?Not recommended.I think I&#x27;ll find the answer here at Penn State University&#x27;s Department of Food Science.John Hayes: We all study food. So you have psychologists and microbiologists and engineers.David Pogue: I&#x27;m here to see John Hayes. He knows a thing or two about the active ingredients in these.John Hayes: So when you went and tasted them, what did you experience?David Pogue: Oh, man. My gut twisted, my tongue burned, my flesh burned, I cried. I got red, my nose ran.It&#x27;s like putting your tongue on the stove and leaving it there.John Hayes: That was an aversive response. This plant has evolved a chemical called capsaicin and the reason it makes that is to keep animals from eating the chili pepper.David Pogue: Oh, man. The chili festival people never got that message. And we&#x27;re just a really stupid species?John Hayes: Exactly. We&#x27;re one of the only species that learns to like that sensation.David Pogue: Ultimately, pepper plants are playing a pretty good trick on humans as well. Capsaicin really is a key ingredient. It has a long spindly tail attached to a ring.John Hayes: That ring end fits into a specific receptor that&#x27;s expressed all over your body.David Pogue: That&#x27;s just our tongue.John Hayes: Not just your tongue.David Pogue: Oh, man.John Hayes: This receptor, this lock, is actually a heat pain sensor.David Pogue: Normally, the receptor called TRPV1, activates when it in contact with something over 106 degrees. The result is a pain message to the brain.Ouch! Something&#x27;s hot!John Hayes: It&#x27;s a warning signal to tell your body danger.David Pogue: And here&#x27;s the tricky part. When you eat peppers, those capsaicin keys fit into the heat pain receptors in your mouth, altering their sensitivity.John Hayes: So what the capsaicin does is it fits into this molecular thermometer and it lowers the temperature at which it activates it.David Pogue: Like a changed thermostat, they now activate at body temperature, sending a false signal that&#x27;s identical to the one your brain would receive if you ate something literally burning hot.It lowers the temperature at which we feel burning pain.John Hayes: Yes.David Pogue: But it&#x27;s not actually burning us?John Hayes: Correct.David Pogue: I&#x27;m not going to see scar tissue-John Hayes: No.David Pogue: No matter how hot it is, it&#x27;s all a fake out?John Hayes: Absolutely.

The chemical that makes chili peppers so hot evolved to keep animals from eating the plants, but humans have learned to like the sensation.

Topic: Body & Brain

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