On the request of the Louvre Museum, Mona Lisa's portrait was digitised with Lumiere Technology's high-resolution multispectral camera. The data from this digitisation revealed for the first time the spolvero (a drawing transfer technique) of the portrait. These discoveries change the history of this iconic symbol of Western painting because they are proof that a preparatory drawing was employed. These discoveries were possible because the multispectral camera produces high-resolution images of 13 filters, including 3 IR filters with a high signal-to-noise ratio and optimal spatial resolution. The images are processed with the layer amplification method (L.A.M.), which amplifies weak signals and thus reveals new details. A test board was made to compare the L.A.M. with traditional IR reflectography.