Researchers at the Delft University of Technology in The Netherlands, in collaboration with the University of Antwerp in Belgium, have discovered a painting by Dutch artist Vincent Van Gogh that was hidden behind another work of his, Patch of Grass (1887), owned by the Kröller-Müller Museum, also in Holland. The discovery was possible thanks to the use of a particle accelerator applied to an X-ray beam that was focused on the painting to measure the fluorescence of the layers of paint, which are differentiated by the chemical element each contains. The application of this technique permitted the individual registry of lead atoms, mercury, and other components found in the pigments, achieving that the top layers of the visible painting distorted the paint of the work underneath to a lesser degree, thus rendering it possible to reveal the portrait ¿ previously hidden ¿ of a woman. Prior research had managed to gather data describing certain subtle traces that formed a head. Nevertheless, it was not until the new technique was applied when the great discovery was made. According to research by the Delft University of Technology, Van Gogh usually reused canvases with previous paintings and painted upon these his new works. It is believed that approximately one third of Van Gogh¿s earlier works contain other images underneath.