Here’s what you need to know about the SARS-CoV-2 virus and the disease it causes, called COVID-19.

UPDATE: Preliminary studies suggest the coronavirus spreads from people with no symptoms. A March 17 study shows the virus can remain viable in aerosols for 3 hours, on cardboard for up to 24 hours, and on plastic and stainless steel for 2 to 3 days.

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.

A neurologist uses carefully-timed pulses of noise to boost the size of brain waves responsible for good-quality sleep—and potentially better memory.

To measure the brain’s ability to form completely new memories, researchers teach kids made-up words for novel objects.

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?

Using a training method called "operant conditioning," or clicker training, this traveling troupe of cats have learned an impressive array of tricks.

It's tough to tell how a cat is feeling just by watching its facial expressions. Can science be used to detect more subtle facial changes that reveal cats' emotions?

Researchers use brain imaging to figure out whether dogs love us—or if they just want treats.

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. And analyzing dogs’ brain activity and genes may even help answer whether dogs are in it for the food—or if they really love us.

A researcher uncovers 30,000-year-old skulls from Europe, which appear to be halfway between those of wolves and domestic canines. But do the skulls actually belong to the ancestors of today's dogs?

Five stories high and emerging from the Taylor Glacier in the Dry Valleys of Antarctica, Blood Falls seeps into an ice-covered body of water called Lake Bonney. It’s one of the continent’s most enigmatic natural features and has fascinated scientists for decades. What makes it red? Does it always flow? And can anything actually survive near it?

A lake in the Arctic has a lot to say about our planet's fluctuating temperatures over the last 34 million years. Play NOVA's Polar Lab to see how.

Carbon dioxide is an odorless, invisible gas. If we could see that carbon as a solid material on the ground, that might change our perspective on the amount of carbon we emit into the atmosphere. Play NOVA’s Polar Lab to see what effects all that CO2 is having on our planet’s poles.

To illustrate how the coastline might look if Earth's climate continues to warm, paleontologist Kirk Johnson and geologist Maureen Raymo search for 3-million-year-old clams in a Virginia quarry miles offshore.

When fossil fuels are burned, they release carbon dioxide, an invisible and odorless gas, into the atmosphere. What would happen if carbon emerged from our car tailpipes as a solid?

Following a trail of fossils found in all the wrong places–beech trees in Antarctica, redwoods and hippo-like mammals in the Arctic–NOVA uncovers the bizarre history of the poles, from miles-thick ice sheets to warm polar forests teeming with life.

Jakobshavn is Greenland's biggest glacier. And over the past 20 years, it's receded dramatically. Play NOVA's Polar Lab to learn what's behind that change.

Earth's climate has slowly fluctuated between cold and hot periods for millions of years. Today, humans are greatly accelerating that process.

Think you know what the Arctic looked like during the Eocene Epoch? Play NOVA’s Polar Lab to find out: You might be surprised by the plants and animals that used to call it home.