A historiated initial from a book of hours: a scene inside a letter, tempera and burnished gold on vellum, an ivy-leaf border with gold bezants, blackletter text and a drollery in the margin. Strictly, "illuminated" means gold or silver is present, not merely that the page has pictures.
By 1400 these were made in commercial Paris workshops, not monasteries, and the figure has the Gothic sway: slender, weight on one hip, animated face. Gold went down first and was burnished, then colour, then shadow, then the ink border, because gold leaf cannot be laid over paint.
A vellum ground with its grain, the big initial and the leafy border are drawn once and cached. The figure is painted flat in tempera colours inside a fine dark contour, with the collar and placket picked out in gold rather than ink, and sits where the saint usually stands in the letter.