The meeting
- Location: Havana's José Martà International Airport, Cuba
- First such meeting since the two branches of Christianity split in the 11th century
The Russian Orthodox Church*
- The largest arm of the Eastern Orthodox church
- Estimated membership of more than 85 million
Roman Catholicism*
- One of the three major branches of Christianity, among with Eastern Orthodoxy and Protestantism
- Estimated membership of nearly 1.1 billion
*Encyclopaedia Britannica
Pictures: Pope Francis boards an airplane at Rome's Fiumicino airport on his way to Cuba.
Apostolic Nuncio, Archbishop Antonio Mennini, and the Diocesan Bishop of the Russian Orthodox, Archbishop Elisey of Sourozh, say they are joining believers around the world in lifting the summit up in prayer.
In the first meeting of it's kind, Pope Francis and Patriarch Kirill are also understood to be signing a declaration in Cuba's capital city, Havana.
Cuba is a significant location for the Pope who has been thanked for his role in improving relations between the country and the United States of America.
Archbishop Antonio Mennini and Archbishop Elisey of Sourozh released a joint message which said: "...this epochal gesture it is offering to humanity - in this moment of severe tensions and conflicts - an extraordinary testimony, unique - of how it is possible to rediscover today - the way of peace and unity. A testimony which, after all, by the will of God is placed in the journey of grace which both Churches are making.
"This meeting doesn't mean that problems between the two Churches have disappeared - they continue to exist and respectful diplomacy and theological commissions will continue to work in order to resolve them - but it marks a new beginning, concentrated on sharing the sufferings of entire peoples, and in particular of Christian communities in the Middle East, which ask help and solidarity and a preoccupation with the defence of Christian values.
"...we are confident that this meeting will be of great social value also for nonbelievers, becoming a moment of rejoicing for respectful populations, as the Popes and the Patriarchs in history prayed for years, during which they longed for this.
"But it will also require the work of ecclesiastical communities, to regain consciousness of what this would mean: a way to discover the true love donated by Christ, which precedes every division and burns resentments, divisions, recrimination, misunderstandings and mutual sufferings.