The article of this title, by Jo Ann Caplin, published in the Spring 2011 issue of the popular science magazine “Chemical Heritage” (The Magazine of the Chemical Heritage Foundation), explores the question of whether the small portrait on vellum known as “La Bella Principessa” is a work by Leonardo da Vinci. Caplin discusses how conservators and art historians have interpreted multispectral images of the work in their consideration of its attribution.