Zachary Crockett at Priceonomics has looked into the history of the symbol.

He says that there are relics resembling the heart shape from 3000 BC. But these shapes stood for ivy or fig leaves, not the heart. It wasn’t until several centuries later that the heart became a symbol representing “love.”

But the problem was, they didn’t really know what the heart looked like partially because the Catholic church prohibited autopsies. So when artists tried to draw the heart as a symbol of love, like in this French manuscript from 1250 it looked … like this.

By the time detailed anatomical drawings appeared, like those of Leonardo Da Vinci in the early 16th century, the simplified symbol had already taken root. It became a popular image in Catholic symbolism as well as secular things like decks of cards.

Eventually New York City’s 1977 campaign turned the heart symbol into a verb, ”I ♥ New York!”

Now it’s used in everything romantic: Valentine’s Day cards, emojis, chocolate. But you can also find it in video games, on Twitter, and in ads for heart healthy food.

It might be a poor likeness for the human heart, but that’s what makes it such an enduring and versatile symbol.

You can get more videos like these by subscribing to the Vox YouTube channel.

That’s cool!

Or maybe your feminism says we should reclaim Valentine’s Day to celebrate all kinds of love between all kinds of people, including close friendships.

That’s cool too!

Or maybe no matter what you think of Valentine’s Day (or feminism), you’d still enjoy sending some fun cards to your feminist friends or significant other(s) this February 14.

Either way, we’ve got you covered.

To learn more about how Čolak overrode his instincts to master the art of oxygen deprivation, watch above. You can get more videos like these by subscribing to the Vox YouTube channel.

There were the requisite nods to his major victories: Obamacare, the Iran deal, Cuba, and curbing greenhouse gas emissions.

But the most memorable moments were those in which the president urged Americans to resist the politics of Donald Trump and others who seek to capitalize on voters’ anxiety:

When politicians insult Muslims, whether abroad or our fellow citizens, when a mosque is vandalized, or a kid is called names, that doesn’t make us safer. That’s not telling it like it is. It’s just wrong. It diminishes us in the eyes of the world. It makes it harder to achieve our goals. And it betrays who we are as a country.

Toward the end of his speech, Obama revisited some of the themes from the 2004 speech at the Democratic National Convention that made him a household name. In that speech, he said, “There’s not a liberal America and a conservative America; there’s the United States of America.” In his final State of the Union, Obama said of his inability to bridge the partisan divide, “It is one of the few regrets of my presidency.”

But Obama wasn’t hopeless. He called on Americans to exercise their right to vote, and on Congress to end the practice of gerrymandering. A year from today, he said, he’ll be a citizen too:

A year from now, when I no longer hold this office, I’ll be right there with you as a citizen—inspired by those voices of fairness and vision, of grit and good humor and kindness that have helped America travel so far. Voices that help us see ourselves not first and foremost as black or white or Asian or Latino, not as gay or straight, immigrant or native born; not as Democrats or Republicans, but as Americans first, bound by a common creed. Voices Dr. King believed would have the final word—voices of unarmed truth and unconditional love.

Read the full text of the speech here.

Guinea worm disease — a terrible parasite that once affected millions in developing countries — may not be long for this world.

The Carter Center announced Wednesday it documented just 22 cases of Guinea worm in 2015. That’s an 83 percent decline from the 126 infections in 2014 — the largest annual decline the group has ever seen.

Guinea worm is a painful, debilitating disease

Guinea worm disease (dracunculiasis) is a painful infection, and it’s been around for thousands of years. Once the parasite enters the body it begins to grow, sometimes reaching an entire meter long. From afar, it looks as though it could be a long, thin cord. Removing a Guinea worm has traditionally involved pulling it out of an opening in the skin over several weeks and spooling the parasite around a stick as though it were a string. It’s a tedious process that can result in a secondary infection at the site of the wound.

This is also how Guinea worm spreads: An infected person feels a painful blister forming, typically on the foot. The foot is soaked in water, but that causes the worm to exit the body and burst, leaving hundreds of thousands of larvae in its wake. If this happens in a communal source of water, the cycle begins all over again.

Guinea worm, on its own, is not a fatal disease. But it’s an arduous one that keeps infected individuals from performing daily tasks and supporting themselves. The Carter Center has spent the past three decades implementing community-based education in the affected countries.

Guinea worm used to exist in thousands of African villages. Not anymore.

According to the numbers, these efforts have paid off. In the past year, only four countries reported cases of infection in 20 total villages: Chad, Ethiopia, Mali, and South Sudan. In 1993, 23,735 villages experienced the disease.

Ethiopia reported three Guinea worm cases last year, and there’s optimism that there won’t be any in 2016. In Chad, there have been reports of domestic dogs contracting Guinea worm. This is unusual since the parasite is typically not found in dogs. But it seems like dogs have been eating raw fish infected with Guinea worm larvae.

Humans cause other challenges too. “Guinea worm reductions in South Sudan and Mali in 2015 are even more remarkable because both countries have significant insecurity or civil unrest and had the largest number of cases in 2014,” said Dr. Ernesto Ruiz-Tiben, director of the Carter Center’s Guinea Worm Eradication Program, in a press release.

Jimmy Carter is the person to thank

After President Jimmy Carter left the Oval Office, his foundation, the Carter Center, began a campaign to eradicate Guinea worm disease. Since there is no current treatment or vaccine for Guinea worm disease, the center focused on public health preventive strategies to stop the disease from spreading in the first place.

It implemented filtering to make sure water is free from larvae, and the organization employed community members to ensure infected people were not going near any water sources. When reported cases do occur, the center prevents the infection from spreading by keeping close watch on outbreaks.

Today the end is near, and Carter is close to reaching the goal he set three decades ago. Experts are hopeful that there will soon come a time when reports of infection come to a complete stop. Once this happens, Guinea worm would be the first parasitic disease that has ever been eradicated — an amazing public health feat for the 21st century.