Van Gogh's Patch of Grass.

I just think this is interesting. Undated handout picture shows a painting underneath Van Gogh's famous work 'Patch of grass' in Hamburg. Scientists have made a coloured view of an early rejected painting underneath Vincent van Gogh's 'Patch of Grass' painting, using advanced X-ray techniques, a Dutch university said on Wednesday.

The very detailed image shows the face of a woman and may give art historians a better understanding of the way Van Gogh developed as a painter.

"It is estimated that one third of Vincent van Gogh's early paintings have been painted on top of existing ones. Van Gogh literally recycled his own canvasses," scientist Joris Dik of the Delft University of Technology said.

Conventional X-ray techniques give a colorless, partial view of the hidden painting and only show vague contours of a person behind 'Patch of Grass', the university said.

By recycling his work Van Gogh painted many layers over the original painting but the scientists managed to scan all the different elements in those layers of the relevant area with X-ray fluorescence.

"We can make a virtual 3-dimensional model of the painting and start to peel off all the layers one by one. Then we get a nice detailed view of the hidden face," Dik said.

Van Gogh painted 'Patch of grass' in 1887 in Paris and it hangs in the Kroller-Muller museum in the Dutch eastern city of Otterlo.