The very fragile portraits are closely guarded in the medal cabinet of Hôtel Turgot. Karen Schaffers-Bodenhausen published a catalogue raisonné devoted to them in 2018. Her book marks a major advance in our understanding of the collection and addresses the problems inherent in classifying the genre. The miniatures are mainly executed in gouache or water colour on parchment, vellum or ivory (less frequently on card or paper), but they can also be painted in oils on wood or copper. The artists of Flanders and Holland in the sixteenth and seventeenth centuries preferred the latter technique, making the boundary between small portraits and miniatures difficult to define.