Amadeo Modigliani led a bohemian life in Paris, but the now famous artist had difficulty selling his art. His nudes were controversial. To save money, he often reused canvases. His "Nude with a Hat" from 1908, which he had already painted on both sides, had one portrait that was upside down. Curators at an Israeli museum have now discovered three more sketches under the painting's surface.

Short of money, Vincent van Gogh used the backs of his canvases, as in his painting "Head of a peasant woman with white cap." Hidden under several layers of glue and cardboard, a self-portrait was discovered using X-rays. It shows a man with a scarf and hat, under which a left ear is clearly visible. This means he must have drawn himself before he cut off his ear in 1888.

Amsterdam's Rijksmuseum closely examined Rembrandt's most famous painting over the past two years, using state-of-the-art technology. It turned out that Rembrandt first made a sketch on the canvas, painted over it and made several changes as he was going along. "We have discovered the genesis of 'The Night Watch,'" director Taco Dibbits said, calling it a "breakthrough."

People are familiar with Johannes Vermeer's "Girl Reading a Letter at an Open Window" (ca. 1657-1659) in its version on the left. Two years ago, researchers discovered a naked cupid figure that had been painted over. The painting, cupid and all, is on display in the Dresden exhibition "Johannes Vermeer. On Reflection" in its original state until January 2, 2022.

Last year, people were surprised at a discovery in the Ghent altarpiece made during restoration work. The Flemish painter Jan van Eyck (about 1390 to 1441) had not painted the lamb as shown on the left, but actually as seen on the right, with a narrow snout and a piercing, downright human-like gaze. The uncovered original was mocked in social media.

The version we see of Michelangelo's "Last Judgement" (1534-1541) in the Sistine Chapel does not correspond to the original. The figures he painted around Jesus Christ were stark naked. His contemporaries felt that was obscene, so they commissioned his student Daniele da Volterra to add pants to the nude figures. He went down in history as "braghettone" (the breeches painter).

Vincent van Gogh painted over many of his pictures. Money was too tight to keep buying new canvases. In 1886, he painted "Still Life with Meadow Flowers and Roses" over two half-naked wrestlers he had created at the Antwerp Art Academy (right). It wasn't until 2012 that the flower painting was clearly attributed to van Gogh.

More painted-over works by van Gogh: the painting "Wild Vegetation" (bottom left) was discovered under "Ravine" (top left). The two paintings were created four months apart. In 2008 researchers used special X-ray technology to find a portrait of a woman under his painting "Grasgrond" (right). They were able to reconstruct the dark portrait in great detail.

Thrifty, Pablo Picasso once used a canvas for "La Misereuse accroupie" (1902) that had already been painted on by an unknown artist. In 2018, a Canadian research team discovered a landscape and a hand underneath the woman with the blanket. Picasso even used the existing lines for his painting.

For almost a century, Max Pechstein's "Lady with Hat" (1910) was hidden behind a flower still life. Pechstein probably canceled out the original with its bright colors because he wasn't happy with it. He preferred to hide what nowadays is seen as Expressionism and considered worthy of protection.

Swiss painter and sculptor Alberto Giacometti (1901-1966) painted over his pictures again and again, not only out of lack of money but because he was dissatisfied with his work. When he painted, he cursed, lamented, and started over again. It took him 18 days to paint the portrait of his friend James Lord.

"I dream of painting an invisible picture," Georg Baselitz said in 2013. But how? By making it disappear under layers of black paint. "Joseph Beuys simply placed the painting with its back to the viewer, preserving the mystery. That's roughly how I imagine it," he said — an entirely different approach from that of his colleagues over the centuries.