miniature

1.  A painting or drawing in an  illuminated manuscript. Web resource here.

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2.  A very small painting, especially a portrait, on ivory, vellum, or other material.

Anguissola Miniature SelfSofonisba Anguissola. Miniature self-portrait mounted as a pendant. Varnished watercolor on parchment.  Ca. 1554. Museum of Fine Arts, Boston.