Painted on a canvas fixed to a circular, convex wooden shield, Caravaggio’s (1571–1610) Medusa carries a dual mythic charge. The two known versions—one from 1596 and the other circa 1597—freeze the instant right after Perseus slays Medusa, depicting her severed head, blood spurting, snakes writhing, her features locked in astonished agony. The shield form echoes Perseus’s mirrored device, used to confront Medusa without meeting her deadly gaze. Caravaggio enhances this symbolism with a clever technical gambit: beneath the paint he built up preparation layers (including one intended to heighten reflectivity), so that the head appears to project outward from the convex surface—a subtle optical illusion demanding the viewer’s participation.