The Jagiellonians were among the most important dynasties in Europe in the 15th and 16th centuries. Their territorial reach extended from the Baltic to the Adriatic and as far as the Black Sea and their reign covered a noteworthy period of political and cultural change, which they themselves were instrumental in shaping.1 Their capital Cracow and its university, founded in 1364, developed into an important trade and financial centre, which laid the foundations for the wealth of the dynasty. The long-established policy of the Jagiellonians to create marriage alliances with princes of the Holy Roman Empire, creating closer ties within the Christian West, meant that the two princesses that this chapter discusses, Zofia (1522-1575) and Katarzyna (1526-1583), became Duchess of Braunschweig-Wolfenbüttel and Queen of Sweden respectively. They were two of the five children of Zygmunt I the Old, King of Poland (1467-1548), and his second wife Bona Sforza (1494-1557). Their siblings were Izabella, later Queen of Hungary (1519-1559), Zygmunt II August (1520-1572), who succeeded his father as king of Poland, and Anna (1523-1596), later Queen of Poland. By their father’s first wife, Barbara Szapolyai (1495-1515), they had a half-sister, Jadwiga (1513-1573), who became Electress of Brandenburg. As this chapter will show, Zofia and Katarzyna grew up in Cracow in a sophisticated centre of Renaissance culture which synthesised influences from the south, the east and the west, so that, when they married, they facilitated the rapid development of cultural trends in their new homes.