A portrait miniature is a miniature portrait painting, usually executed in gouache, watercolor, or enamel. Portrait miniatures developed out of the techniques of the miniatures in illuminated manuscripts, and were popular among 16th-century elites, mainly in England and France, and spread across the rest of Europe from the middle of the 18th century, remaining highly popular until the development of daguerreotypes and photography in the mid-19th century. They were usually intimate gifts given within the family, or by hopeful males in courtship, but some rulers, such as James I of England, gave large numbers as diplomatic or political gifts. They were especially likely to be painted when a family member was going to be absent for significant periods, whether a husband or son going to war or emigrating, or a daughter getting married.

Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C. The powder melts, flows, and then hardens to a smooth, durable vitreous coating. The word vitreous comes from the Latin vitreus, meaning "glassy".