national research and restoration laboratory in the basement of the famous museum. here, the curator began studying the fragile drawing to try to discover its origins. after infrared, ultraviolet and a host of other analytical techniques, they determined from the paper and other indicators that the sketch is indeed from da vinci s era and region of italy. but what intrigued him most was the thousands of tiny holes in the drawing. evidence of a renaissanceed pri. when they laid out the holes on the computer, they came close to exactly matching two other paintings, one in russia and one in a private collection, which are known to have at least come from da vinci s workshop and perhaps were done by da vinci. a step further towards authenticating the nude mona lisa. the mystery still remains.