Saints Cyril and Methodius were two Byzantine brothers born in Thessalonica in the 9th century. Part of a prominent Christian family, their father was Greek and their mother was Bulgarian. In 860 Cyril and Methodius went as missionaries to what is today the Ukraine, spreading Christianity among the Slavic peoples of Bulgaria, Great Moravia and Pannonia.
They are credited with devising the Glagolitic alphabet. At the request of the Moravian prince Rastislav, they began to transcribe religious books from Greek into Old Bulgarian. Their alphabet is seen as the precursor to Cyrillic, which was named after Cyril. Today most of the Slavic countries, including Russia, still use an extension of that alphabet.