From the museum website
Mannerism, a refined artistic style originating in Italy, took hold in Flanders in the 16th century, bringing with it a new repertoire of subjects, techniques, and sensibilities. It coincided with the rapid development of printmaking, especially engraving, by Flemish artists. Master engravers such as Pieter Bruegel the Elder and Hendrick Goltzius transformed the role of prints from being mere book illustrations to works of art in their own right, avidly collected by the newly prosperous merchant class.