Saints Cyril and Methodius are most often depicted together in art and other renderings. These two future saints were brothers, born in Thessalonika. These two brothers demonstrated remarkable intelligence and young men, so it wasn't surprising to see that they became very successful as adults; Methodius became a governor in a Slav province, Cyril a scholar and philosopher at the University of Constantinople. Despite the trappings of their success and the material world, they felt the pull of their Father in Heaven and left all the fame and fortune behind in His service.
Cyril and Methodius were almost immediately recognized for thier intelligence and were sent to the lands of Russia and Moravia where they learned the languages and customs so they could teach the faith. The news of their success spread to Rome. In the year 872 A.D., Pope Nicholas I called for them, but the pope died before they reached Rome. Pope Adrian II, the successor to Pope Nicholas I, was so impressed by what he had heard and seen of the two brothers that he planned on making them both bishops of the Church. Saint Cyril died before he could be consecrated as bishop. Methodius continued with his missionary work, even in the face of opposition of other bishops. At one point in time, he was even thrown into prison and it took the intervention of the pope to free him.
For their missionary work, these two brothers became known as the "apostles of the Slavs" and are patron saints of the Unity of the East and West Churches.