A previously unknown self-portrait of Vincent van Gogh - complete with pre-severed ear - has been discovered, say experts.
The artwork shows a bearded sitter in a brimmed hat with a neckerchief loosely tied at the throat.
His left ear, which he famously cut off in 1888, is clearly visible.
Believed to have been hidden from view for more than a century, the sketch was unearthed after an X-ray was taken of another of Van Gogh's works - Head of a Peasant Woman (1885) - and it was found on the back of the canvas, hidden by layers of cardboard.
Van Gogh was known for reusing canvas to save money by turning it round and working on the opposite side.
The extraordinary find by the National Galleries of Scotland is believed to be a first for a UK institution.
It is thought to be from his early work and his first exploration of self-portraits, which he later became known for.
The layers of cardboard and glue were thought to have been applied ahead of an exhibition in the early 20th century.
Visitors to the forthcoming exhibition A Taste for Impressionism at the Royal Scottish Academy, Edinburgh, will be able to see the sketch as an X-ray image through a specially crafted lightbox.
While it may be possible to separate the two pieces, the process of removing the glue and cardboard will require delicate conservation work. Research is taking place as to how that can be done without harming Head of a Peasant Woman.
The discovery has been described as "thrilling" by Professor Frances Fowle, senior curator of French art at the National Galleries of Scotland.
She had been queuing outside a fish shop when she got a text from her colleague telling her the extraordinary news.
She said: "Moments like this are incredibly rare.
"We have discovered an unknown work by Vincent van Gogh, one of the most important and popular artists in the world.
"What an incredible gift for Scotland, and one that will forever be in the care of the National Galleries."
Lesley Stevenson, senior paintings conservator at the National Galleries, said: "This is a significant discovery because it adds to what we already know about Van Gogh's life.
"There is lots to think about with regards to the next steps, but for us it is another little nugget to get us a little bit closer to an incredible artist.
"Knowing that it's there in a painting, that's in the National Galleries of Scotland in a collection that belongs to the people of Scotland, is incredibly important and significant."
The exhibition, A Taste for Impressionism, begins on 30 July and runs until 13 November.