In this two-hour special, renowned paleontologist Kirk Johnson takes us on an epic adventure through time at the polar extremes of our planet. Following a trail of strange fossils found in all the wrong places—beech trees in Antarctica, hippo-like mammals in the Arctic—Johnson uncovers the bizarre history of the poles, from miles-high ice sheets to warm polar forests teeming with life. What caused such dramatic changes at the ends of the Earth? And what can the past reveal about our planet’s climate today—and in the future?

Dogs have long been dependable companions by our sides. But it wasn’t always that way, and a look at their closest living relative, the wolf, makes it clear why. Research into dog domestication and intelligence offers clues into what the human-dog relationship is all about. And analyzing dogs’ brain activity and genes may even help answer the question of whether dogs are in it for the food—or if they really love us.

Worshipped as a goddess, condemned as satanic, and spun into a stunning array of breeds, cats have long fascinated humans. But did we ever really domesticate them? And what can science tell us about our most mysterious companions?

From fruit flies to whales, virtually every animal sleeps. But why? Why do we need to spend nearly a third of our lives in such a defenseless state? Scientists are peering more deeply into the sleeping brain than ever before, discovering just how powerful sleep can be, playing a role in everything from memory retention and emotional regulation to removing waste from our brains. So why are we getting so little of it?

Cuban scientists develop their own biotech industry, including lung cancer vaccines that may give new hope to patients around the world.

The mysteries of fat and its role in hormone production, hunger and pregnancy.

The coronavirus SARS-CoV-2 has upended life as we know it in a matter of mere months. But at the same time, an unprecedented global effort to understand and contain the virus—and find a treatment for the disease it causes—is underway. Join the doctors on the front lines of the fight against COVID-19 as they strategize to stop the spread, and meet the researchers racing to develop treatments and vaccines. Along the way, discover how this devastating disease emerged, what it does to the human body, and why it exploded into a pandemic.

Eagles dominate the skies. But what makes these predators so special? Researchers study one special bird—and stunning up-close footage reveals her exceptional strength, eyesight, and flying skills. With intimate access to a new bald eagle family, NOVA takes you into the nest to witness the drama of chicks struggling to survive.

With an extraordinary new technology called CRISPR, we can now edit DNA—including human DNA. But how far should we go? Gene-editing promises to eliminate certain genetic disorders like sickle cell disease. But the applications quickly raise ethical questions. Is it wrong to engineer soldiers to feel no pain, or to resurrect an extinct species? And is there harm in allowing parents to choose their child’s features, like eye color or height? The scientists who pioneered human genome studies and CRISPR grapple with these questions.

Who says you need brains to be smart? Extremely primitive life-forms called slime molds can navigate mazes, choose between foods, and create efficient networks—no brain required. New research on these organisms, which are neither plant nor animal, could help reveal the fundamental rules underlying all decision making.

Writing shaped our world and the rise of human knowledge, from the trading of goods to tales of ancient goddesses and kings. Follow the evolution of the written word, from 4,000-year-old carvings in an Egyptian turquoise mine to modern-day alphabets.

Just as writing changed the course of human history, the evolution of paper and printing revolutionized the spread of information. The printing press kicked off the Industrial Revolution that fast-tracked us to the current digital age. But as the 4,000-year-old tradition of penmanship falls out of favor, should we consider what might be lost in this pursuit of ever more efficient communication?

For animals in Mozambique’s Gorongosa National Park, the normal balance of competition and predation was upended when a war wiped out the top predators. The remaining animals didn’t simply grow in numbers—they began behaving in unusual ways, veering outside their typical territories and feeding patterns. Could it be that it’s not just predators’ kills that keep other populations in check, but also the fear they inspire? NOVA joins a team of scientists as they reintroduce wild dogs to Gorongosa to find out if restoring the park’s “landscape of fear” can restore balance to an entire ecosystem.

If spacecraft OSIRIS-REx can grab a piece of an asteroid and bring it back to Earth, scientists could gain great insight into our planet's origins, and even how to defend against rogue asteroids. But NASA only gets three shots at collecting a sample.

As global temperatures continue to rise, scientists are wondering if we need solutions beyond reducing emissions. Enter geoengineering. From sucking carbon straight out of the air to physically blocking out sunlight, the options may seem far-fetched. But as time runs out on conventional solutions to climate change, scientists are asking the hard questions: Can geoengineering really work? How much would it cost? And what are the risks of engineering Earth's climate?

When the roof of Notre Dame Cathedral erupted in flames in April of 2019, firefighters battled for nine grueling hours to save the historic landmark. Still, Paris came alarmingly close to losing more than 800 years of history. Now engineers are in a different race against time: to rebuild the roof and secure the medieval structure of Notre Dame. Underneath the charred scaffolding and vaulted ceilings of the cathedral, scientists study the components of Notre Dame’s iconic structure to puzzle out how best to repair it.