The chapter follows the well-known and well-studied activity of St. Methodius of Thessalonica, the brother of St Constantine, Cyril, who was, after his death in 869, consecrated by the pope the bishop of Pannonia and Moravia, his efforts in creating the “Slavic Church” in those Central European countries in 870–885 and the challenges he faced, mostly according to the information of his Old Slavonic Life, and following the results of the newest scholarly work.