Cyril was born in Thessalonica to Leo, an imperial magistrate, in 826 or 827. He was the youngest of seven. As a child he learned the Slavonic language. When he was 14 years old he was sent to Constantinople to be educated and was companion to the young Emperor, Michael III. In those years Cyril was introduced to the various university disciplines, including dialectics, and his teacher was Photius. After refusing a brilliant marriage he decided to receive holy Orders and became "librarian" at the Patriarchate. Shortly afterwards, wishing to retire in solitude, he went into hiding at a monastery but was soon discovered and entrusted with teaching the sacred and profane sciences. He carried out this office so well that he earned the nickname of "Philosopher". In the meantime, his brother Michael (born in about 815), left the world after an administrative career in Macedonia, and withdrew to a monastic life on Mount Olympus in Bithynia, where he was given the name "Methodius" (a monk's monastic name had to begin with the same letter as his baptismal name) and became hegumen of the Monastery of Polychron.
Attracted by his brother's example, Cyril too decided to give up teaching and go to Mount Olympus to meditate and pray. A few years later (in about 861), the imperial government sent him on a mission to the Khazars on the Sea of Azov who had asked for a scholar to be sent to them who could converse with both Jews and Saracens. Cyril, accompanied by his brother Methodius, stayed for a long time in Crimea where he learned Hebrew and sought the body of Pope Clement I who had been exiled there. Cyril found Pope Clement's tomb and, when he made the return journey with his brother, he took Clement's precious relics with him. Having arrived in Constantinople the two brothers were sent to Moravia by the Emperor Michael III, who had received a specific request from Prince Ratislav of Moravia: "Since our people rejected paganism", Ratislav wrote to Michael, "they have embraced the Christian law; but we do not have a teacher who can explain the true faith to us in our own language". The mission was soon unusually successful. By translating the liturgy into the Slavonic language the two brothers earned immense popularity.
However, this gave rise to hostility among the Frankish clergy who had arrived in Moravia before the Brothers and considered the territory to be under their ecclesiastical jurisdiction. In order to justify themselves, in 867 the two brothers travelled to Rome. On the way they stopped in Venice, where they had a heated discussion with the champions of the so-called "trilingual heresy" who claimed that there were only three languages in which it was lawful to praise God: Hebrew, Greek and Latin. The two brothers obviously forcefully opposed this claim. In Rome Cyril and Methodius were received by Pope Adrian ii who led a procession to meet them in order to give a dignified welcome to St Clement's relics. The Pope had also realized the great importance of their exceptional mission. Since the middle of the first millennium, in fact, thousands of Slavs had settled in those territories located between the two parts of the Roman Empire, the East and the West, whose relations were fraught with tension. The Pope perceived that the Slav peoples would be able to serve as a bridge and thereby help to preserve the union between the Christians of both parts of the Empire. Thus he did not hesitate to approve the mission of the two brothers in Great Moravia, accepting and approving the use of the Slavonic language in the liturgy. The Slavonic Books were laid on the altar of St Mary of Phatmé (St Mary Major) and the liturgy in the Slavonic tongue was celebrated in the Basilicas of St Peter, St Andrew and St Paul.
Unfortunately, Cyril fell seriously ill in Rome. Feeling that his death was at hand, he wanted to consecrate himself totally to God as a monk in one of the Greek monasteries of the City (probably Santa Prassede) and took the monastic name of Cyril (his baptismal name was Constantine). He then insistently begged his brother Methodius, who in the meantime had been ordained a Bishop, not to abandon their mission in Moravia and to return to the peoples there. He addressed this prayer to God: "Lord, my God... hear my prayers and keep the flock you have entrusted to me faithful .... Free them from the heresy of the three languages, gather them all in unity and make the people you have chosen agree in the true faith and confession". He died on 14 February 869.
Faithful to the pledge he had made with his brother, Methodius returned to Moravia and Pannonia (today, Hungary) the following year, 870, where once again he encountered the violent aversion of the Frankish missionaries who took him prisoner. He did not lose heart and when he was released in 873, he worked hard to organize the Church and train a group of disciples. It was to the merit of these disciples that it was possible to survive the crisis unleashed after the death of Methodius on 6 April 885: persecuted and imprisoned, some of them were sold as slaves and taken to Venice where they were redeemed by a Constantinopolitan official who allowed them to return to the countries of the Slavonic Balkans. Welcomed in Bulgaria, they were able to continue the mission that Methodius had begun and to disseminate the Gospel in the "Land of the Rus". God with his mysterious Providence thus availed himself of their persecution to save the work of the holy Brothers. Literary documentation of their work is extant. It suffices to think of texts such as the Evangeliarium (liturgical passages of the New Testament), the Psalter, various liturgical texts in Slavonic, on which both the Brothers had worked. Indeed, after Cyril's death, it is to Methodius and to his disciples that we owe the translation of the entire Sacred Scriptures, the Nomocanone and the Book of the Fathers.
Wishing now to sum up concisely the profile of the two Brothers, we should first recall the enthusiasm with which Cyril approached the writings of St Gregory of Nazianzus, learning from him the value of language in the transmission of the Revelation. St Gregory had expressed the wish that Christ would speak through him: "I am a servant of the Word, so I put myself at the service of the Word". Desirous of imitating Gregory in this service, Cyril asked Christ to deign to speak in Slavonic through him. He introduced his work of translation with the solemn invocation: "Listen, O all of you Slav Peoples, listen to the word that comes from God, the word that nourishes souls, the word that leads to the knowledge of God". In fact, a few years before the Prince of Moravia had asked the Emperor Michael III to send missionaries to his country, it seems that Cyril and his brother Methodius, surrounded by a group of disciples, were already working on the project of collecting the Christian dogmas in books written in Slavonic. The need for new graphic characters closer to the language spoken was therefore clearly apparent: so it was that the Glagolitic alphabet came into being. Subsequently modified, it was later designated by the name "Cyrillic", in honour of the man who inspired it. It was a crucial event for the development of the Slav civilization in general. Cyril and Methodius were convinced that the individual peoples could not claim to have received the Revelation fully unless they had heard it in their own language and read it in the characters proper to their own alphabet.
Methodius had the merit of ensuring that the work begun by his brother was not suddenly interrupted. While Cyril, the "Philosopher", was more inclined to contemplation, Methodius on the other hand had a leaning for the active life. Thanks to this he was able to lay the foundations of the successive affirmation of what we might call the "Cyrillian-Methodian idea": it accompanied the Slav peoples in the different periods of their history, encouraging their cultural, national and religious development. This was already recognized by Pope Pius XI in his Apostolic Letter Quod Sanctum Cyrillum, in which he described the two Brothers: "Sons of the East, with a Byzantine homeland, of Greek origin, for the Roman missions to reap Slav apostolic fruit" (AAS 19  93-96). The historic role they played was later officially proclaimed by Pope John Paul II who, with his Apostolic Letter Egregiae Virtutis, declared them Co-Patrons of Europe, together with St Benedict (31 December 1980; L'Osservatore Romano English edition, 19 January 1981, p. 3).
Cyril and Methodius are in fact a classic example of what today is meant by the term "inculturation": every people must integrate the message revealed into its own culture and express its saving truth in its own language. This implies a very demanding effort of "translation" because it requires the identification of the appropriate words to present anew, without distortion, the riches of the revealed word. The two holy Brothers have left us a most important testimony of this, to which the Church also looks today in order to draw from it inspiration and guidelines.+