Scientists who started analyzing the painting by the Dutch artist in 2018 found that the background hadn't always been black: Vermeer painted a green curtain that had darkened over time. They also discovered that the girl has thin eyelashes that cannot be seen with the naked eye. Unfortunately, the researchers could not solve the mystery of the women's identity.

Originally, the artist painted cupid into the work in the spot where we now see a green curtain. That the hidden messenger of love existed has been known since 1979, however, in 2019 a museum in Dresden discovered that Vermeer had not painted the green curtain himself and decided it should be removed to reveal the cherub once more.

Most of the iconography in this vibrant work is not fully understood by scholars. The burning candle on the chandelier, for example, suggests that the wedding was a Christian marriage. The dog could be a symbol of marital fidelity. But who are the two figures reflected in the mirror on the back wall? Are they witnesses to the ceremony or is one, perhaps, the painter himself?

According to Vatican researcher Sabrina Sforza Galitzia, there's a secret puzzle in the famous painting, predicting that the end of the world will happen in 4006. What's more, composer Giovanni Maria Pala says he found musical notation encoded in the work, with the hands of Jesus and the apostles and the loaves of bread representing different notes. Da Vinci was known to write musical riddles.

The true identity of the sitter in this iconic work may be one of the greatest mysteries of art history. Who is the woman also known as "La Gioconda"? How did da Vinci manage to make her seem to follow the viewer with her gaze? Whoever she was, her image was once stolen from the museum in 1911 by an Italian waiter who dressed himself as a Louvre janitor and took the painting to Florence.

Although the technique of looking into a mirror while painting a self-portrait was common, it was highly unusual for an artist to actively paint the mirror into the painting. Why Gumpp did this is unknown. Scholars have also pondered a significance between his decision to include three images of himself. Could it, perhaps, be a reference to the Holy Trinity?

In this scene in the Spanish court it is unclear who is the subject, object, spectator and model. Although they stand together, the figures appear isolated in their own worlds. Many mysteries remain: Does the mirror in the background reflect the image of the Spanish royal couple who have come to observe or is it simply a reflection of what is on the artist's easel?

If you look closely, you will discover another silhouette above the head of the man playing guitar in the painting. Researchers found that it is part of a painting underneath the one that meets the eye. Presumably, Picasso painted over an old canvas, but did not completely cover the woman's head. The work hails from Picasso's Blue Period in the early 20th century.

In this painting, the German artist portrayed his 11-year-old daughter, Betty, without showing her face. He thereby created a fascinating (anti)portrait: No matter how long you look, Betty won't turn around. The work is often mistaken for a photograph at first glance; Richter made it a bit blurry, as an out-of-focus snapshot would be.