Leonardo da Vinci may have accidentally invented the first stereoscopic image in history. According to researchers Claus-Christian Carbon and Vera M Hesslinger, his iconic painting of the Mona Lisa can be seen in 3D thanks to another version that was painted side by side while da Vinci was making the original.

X-ray images showed that El Prado's Mona Lisa was painted by an apprentice at the same time of the original. Corrections were made by da Vinci himself.

The body of La Gioconda was shifted in relations to the background, making her body perspective different as well.

Researchers found that this binocular treatment resulted in two different paintings that when combined created a stereoscopic image.