A major international gathering of the Catholic Church is due to begin in the Republic of Ireland later.
The World Meeting of Families will open in Dublin on Tuesday evening with a ceremony of worship and prayer, with thousands of people expected to attend.
It comes ahead of Pope Francis' first tour of Ireland this weekend.
The visit is the first to Ireland by a Pope in almost 40 years and will finish with a Papal Mass at Dublin's Phoenix Park on Sunday.
The World Meeting of Families is held every three years, with thousands of people from across the world gathering for it.
It includes a three-day congress with speakers, workshops and discussions due to address the event's theme of the importance of family in the Catholic faith.
It is the first time the event has been held in Ireland.
All Catholic dioceses in Ireland will mark the launch by ringing bells in each of the 26 diocesan cathedrals.
Pope to attend concert
Pope Francis will arrive in Dublin on Saturday morning for a 36-hour stop in the Irish Republic.
The last time a pontiff visited the country was in 1979, when Pope John Paul II made an appeal for the end all violence and a return to "the ways of peace".
The head of Ireland's Catholic Church has said he expects Pope Francis to meet victims of clerical sex abuse during his visit to Ireland.
On Saturday evening the Pope will attend the Festival of Families concert in Dublin's Croke Park stadium.
More than 70,000 people are expected to take part, with the world-renowned tenor Andrea Bocelli due to perform.
Other acts on the bill include Nathan Carter, Daniel O'Donnell, Moya Brennan, the Begley Family and the Priests.
The pontiff will travel to County Mayo on Sunday morning for a visit to Knock Shrine.
He will return to Dublin for an afternoon mass in front of an estimated 500,000 people in Phoenix Park to close the World Meeting of Families.
Papal visit to Ireland: Itinerary highlights
Saturday 25 August
- 08:15 - Departure by plane from Rome for Dublin
- 10:30 - Arrival at Dublin Airport for official welcome
- 10:45 - Transfer to Áras an Uachtaráin (Irish president's residence)
- 11:15 - Welcome ceremony with President Michael D Higgins
- 12:10 - Arrival at Dublin Castle for meeting with authorities, civil society and diplomatic corps
- 15:30 - Visit to St Mary's Pro Cathedral
- 16:30 - Private visit to the Capuchin Day Centre, a centre for homeless people
- 19:45 - Preside at the Festival of Families at Croke Park stadium
Sunday 26 August
- 08:40 - Departure by plane for Knock
- 09:45 - Arrival at Knock Shrine for visit to the Apparition Chapel and recitation of the Angelus
- 11:15 - Departure by plane for Dublin
- 12:30 - Lunch with the Papal Delegation
- 15:00 - Closing Papal Mass of the World Meeting of Families in Phoenix Park followed by a meeting with the Irish bishops
- 18:30 - Farewell ceremony at Dublin Airport
- 18:45 - Departure by plane for Rome
- 23:00 - Arrival in Rome