With the aid of infrared reflectography, researchers at the National Gallery in London found that Leonardo da Vinci sketched a different motif [red] before he painted The Virgin of the Rocks in the early 16th century.

Nuclear magnetic resonance (NMR) is the same technology found in the MRI (magnetic resonance imaging) scanners used in medicine. To produce a signal read by the NMR machine, the hydrogen atoms in the paint absorb high-frequency radio waves emitted by a magnetic field. Different materials in paintings absorb these radio waves differently, which allows scientists to decipher the stratigraphy, or thickness of layers, of a work of art. In addition, the absorption rate differs with the age of the materials, thereby distinguishing the original from restored sections of paintings.