A new X-ray technique has revealed a previously unknown portrait of a woman by Vincent van Gogh, which was painted over by the artist.
The peasant woman's face was hidden behind the work Patch of Grass, completed by Van Gogh in Paris in 1887.
Scientists Joris Dik and Koen Janssens used high-intensity X-rays from a particle accelerator to scan the painting and reveal the face beneath.
Van Gogh is known to have often reused canvasses to save money.
The identity of the peasant woman in the painting is not known.
The powerful X-ray bombardment caused atoms in the picture's layers of paint to emit 'fluorescent' X-rays of their own, which indicated the chemicals they originated from. That enabled a colour map of the hidden picture to be produced.
The portrait fills a square area measuring 17.5cm by 17.5cm (6.8 by 6.8 inches).
Mr Dik, a materials scientist from Delft University, and Mr Janssens, a chemist from the University of Antwerp in Belgium, published their scientific paper online in the journal Analytical Chemistry.
Image and text by BBC News UK