In Correggio's Holy Night there is no lamp, no moon and no fire. The light comes from the newborn Child, and it is so strong that a shepherd girl shields her eyes. Here is how one Christmas painting taught Europe to paint the dark.

Agnolo Bronzino painted Eleonora of Toledo, wife of Duke Cosimo I de' Medici, in a gold-brocaded gown beside her young son. The cool, flawless surface is the message: a dynasty that expected to last.

Parmigianino painted the Madonna with the Long Neck for a chapel in Parma and died before finishing it. Its stretched Virgin, sprawling child and columns going nowhere defined Mannerism.

Pontormo painted the Deposition from the Cross 1525-1528 as the altarpiece for the small Capponi family chapel in the Florence church of Santa Felicita. The 313 × 192 cm panel is the canonical post-Raphael Mannerist break from High Renaissance composition: ten figures in an unstable vertical pyramid, no Cross visible anywhere, no landscape, no architecture, no perspectival depth.

Four allegorical heads built entirely from blossoms, ripe produce, the harvest, and the bark of a bare tree. What each of Giuseppe Arcimboldo's Four Seasons is actually made of, why a court painter assembled faces from vegetables for the Habsburg emperors, and the imperial message hidden inside the harvest.

After Raphael died in 1520, Italian painting got stranger. Necks lengthened, bodies twisted into spirals, colour grew acidic, space stopped behaving. Reading the painters who closed the High Renaissance — Pontormo, Parmigianino, Bronzino, El Greco — and the movement we now call Mannerism.