Leonardo painted the last supper in the refectory of the convent of Santa Maria delle Grazie by order of Ludovico il Moro, in a period ranging from 1494 to 1497. The artist, painting on the wall, you are not as resistant to the traditional Fresco technique, which requires a quick drafting of color on the plaster is still wet, but wanted to experience an innovative method that would allow him to intervene on dry plaster and, then, to return to work taking care of every detail. Unfortunately the insights of Leonardo proved wrong and soon, for an unhappy combination of causes, the painting began to deteriorate. Over the centuries, as a result, many restorations followed in a desperate attempt to save the masterpiece. In 1999, after over twenty years of work, ended the last conservative intervention that, thanks to the removal of overpaintings, brought to light what remained of the original drafts.