What do we call the medieval art of decorating initials and pages in manuscripts?

The story behind the answer

This was the craft of adorning handwritten books with lavish initials, borders, and small scenes, often highlighted with gold and silver so the page seemed to “glow.” Monks and artisans worked in scriptoria, applying precious pigments like ultramarine from lapis lazuli and delicate gold leaf to elevate sacred texts and signal a patron’s wealth and piety.

It differs from rubrication (red headings or instructions), marginalia (notes or doodles in the margins), and stand-alone miniature painting. Famous examples include the Book of Kells and the Lindisfarne Gospels, where shimmering letters and intricate interlace not only beautified Scripture but also guided readers’ attention and taught through imagery in an age when many were illiterate.