Although schismatic groups in the East can date as far back as the fourth century, they would eventually return to conformity with the Catholic Church in Rome, until the 11th century.
In the year 1054, Christianity experienced, what is today still referred to as, the Great Schism. Church leaders in Constanopole separated from the Roman Holy See, mostly over the authority of the papacy.
As of that point, the patriarch of Constanopole began leading the Eastern Byzentine Churches, later known as the Orthodox Church, which followed the original doctrine of the One, Holy, Catholic and Apostolic Church established by Christ, ironically, with the exception of following the authority of Peter, who was the Rock the Lord establish His Church on, and the Magesterium (the teaching authority of the Bishops, who are the direct descendants of the Apostles by the laying of hands from generation to generation, in union with the pope).
For almost a thousand years, the two sides have never been able to fully restore the relationship.
In an ongoing attempt by the Vatican to restore Christianity to the intent of Christ, who prayed for His Disciples to be one as He and the Father were One, last week, Roman Catholic and Orthodox Church leaders met to discuss the biggest stumbling block between them.