sentences:  Over time, five Patriarchates were established to organize the Christian world, and four of these ancient Patriarchates remain Orthodox today.Orthodox Christianity reached its present form in Late Antiquity (in the period from the 3rd to the 8th century), when the Ecumenical Councils were held, doctrinal disputes were resolved, the Fathers of the Church lived and wrote, and Orthodox worship practices settled into their permanent form (including the liturgies and the major holidays of the Church).In the early medieval period, Orthodox missionaries spread Christianity towards the north, to the Bulgarians, Serbs, Russians and others.