But it doesn't really look like the real thing.

Zackary Crokett at Priceonomics has looked into the history of this.

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 of 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 love New York," replacing the word "love".

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.