The US has discontinued a variety of different currency denominations over the years—including a $100K bill.

Plato's famous allegory of the cave is a metaphor exploring the value of truth over ignorance.

Cats have a mutation that prevents them from tasting sweetness, and goldfish rank among the world's supertasters.

Humans tend to imagine aliens as humanlike, but that's probably unlikely. Three different hypothetical planets show how aliens' bodies could take many forms.

The collapse of gas bubbles in the joint synovial fluid causes 'cracking' knuckles.

Located on Ross Island in Antarctica, Mount Erebus is the southernmost active volcano on Earth and features a lava lake—one of eight known worldwide as of 2026—that erupts regularly.

Humans may have as many as 100,000 to 150,000 individual hairs on our scalps, growing at a rate of roughly 1 centimeter per month.

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

Although the moon passes between the sun and Earth each month, its orbit is tilted by five degrees, preventing Earth from experiencing a solar eclipse each month.

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

'Tulip mania,' the 1630s Dutch craze where rare bulbs were briefly traded like luxury assets, may have been the first financial bubble—and it still shapes markets today.

Lake Sørvágsvatn sits about 32 meters (105 feet) above sea level, but the taller surrounding cliffs create an optical illusion that makes it appear to float much higher above the ocean.

Explore the known asteroids, comets, and spacecraft involved in asteroid studies within our solar system with 'Eyes on Asteroids,' a 3D visualization from NASA.

There are up to 100 trillion microbes in the gut, and maintaining the relative balance in this ecosystem is important for our health.

Watch footage from the moments the Titanic wreck was discovered by a joint US-French research team in 1985.

Listen to audio clips from Hoover, a harbor seal named after its insatiable appetite, who learned to say English phrases such as 'hello there' and 'come over here.'

Apeirophobia is the fear of everlasting life and may stem from the human brain's inability to conceptualize the concept of anything happening beyond what it can project out, such as the concept of an infinite life.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

There are 'YouTube camps' that teach children how to create content for the video platform.

Simulations suggest that a paper airplane launched from the International Space Station would maintain its orientation and gradually descend for 3.5 days before chaotically tumbling down and burning up.

Pregnancy makes someone more attractive to the mosquito species that transmits malaria.

Researchers generally group gut bacteria into six different categories, with varying amounts of these microbes residing in different parts of the digestive tract.

The Berlin Wall physically separated East and West Berlin for nearly three decades, preventing East Germans from fleeing to the West and earning the nickname 'the Iron Curtain.'

Semaglutides, which belong to a class of drugs called GLP-1s, are prescribed for weight loss in combination with diet and exercise because they trigger the release of the appetite-suppressing hormone incretin.

Streaming service Netflix's sound logo 'Tudum' was designed as a key sonic differentiator.

Light takes approximately eight minutes to travel from the sun's surface to Earth, but it takes thousands of years to reach the star's surface from its core—a distance more than 200 times shorter.

'Bibliotherapy' is of increasing interest as a way to improve mental health and help navigate complex life situations—with people immersing themselves in the experiences of fictional characters or nonfiction and self-help books to find relief and gain personal insights.

Explore 3D models of some of the most dangerous viruses, allowing us to understand these and other pathogens in new ways.

Give your memories a place to live and explore the personal stories left by strangers, tied to specific locations, in this interactive map of the world.

Explore Lewis and Clark's 8,000-mile journey in Google Earth.

Use this tool to calculate the dollar value of your parental mental load, from meal planning to coordinating after-school care, then see resources that help generate solutions.

Robert Smalls escaped slavery by piloting a stolen Confederate ship to freedom, then became an influential Black political leader during Reconstruction.

Peek into the love lives of thousands of strangers whom Stanford University researchers have been tracking since 2017 on this interactive page.

Watch President John F. Kennedy's speech on going to the moon

Miracle berries make things that normally taste acidic or sour, such as lemons, taste sweet, like sugar-coated candy, by binding a special protein called miraculin to taste buds.

Sea stars are invertebrates—they lack a backbone—and while most exhibit pentametric radial symmetry due to having five arms radiating from a central disk, some can possess more than 40.

George Lucas used Joseph Campbell's 'hero's journey,' a narrative structure that encompasses the common characteristics of multiple cultures' mythologies, to revise 'Star Wars.'

The animatronic shark from 'Jaws' was a complex machine called 'Bruce.'

Between 2002 and 2012, at least 12 people were killed in the Philippines in incidents related to off-key karaoke singing of Frank Sinatra's 'My Way.'

The world's largest waterfall is in the ocean and is more than three times the height of Angel Falls, the largest waterfall on land.