The architects of the Good Friday Agreement have gathered in Belfast to mark 20 years since the Troubles ended.
But what exactly was the agreement, and why was it so important for Northern Ireland?
What is the Good Friday Agreement?
Its official name is the Belfast Agreement, however because it was reached on Good Friday, 10 April 1998, it is also often referred to as the Good Friday Agreement.
It was an agreement, between the British and Irish governments and most of the political parties in Northern Ireland, about how Northern Ireland should be governed. It brought an end to the 30-year conflict known as 'the Troubles'.
It legitimised the desire for a United Ireland while acknowledging that the majority in Northern Ireland wanted to remain in the United Kingdom.
The agreement called for the establishment of three “strands” of administrative relationships that exist within and between the islands of Britain and Ireland.
The Northern Ireland Assembly and Executive were set up so that the elected political parties could share power. The Assembly is located at Stormont, just outside Belfast.
The North South Ministerial Council was set up to develop co-operation between both parts of Ireland.
The British-Irish Council was set up to promote the relationship between Ireland and Britain.
What were 'the Troubles'?
The Good Friday Agreement ended the 30-year sectarian conflict known as 'the Troubles' in which more than 3,000 lives were claimed.
The British Government ordered the deployment of troops to Northern Ireland in August 1969, signalling the start of the Troubles.
The troops were supposed to combat an increase in sectarian violence during the traditional Protestant marching season.
Although the British troops were intended to be neutral peacekeepers, many in Northern Ireland saw them as a tool of the Unionist Government.
Subsequently, the Provisional Irish Republican Army, (PIRA) which had formed in 1969, increased attacks in the region. The PIRA was fighting for a United Ireland.
In response to PIRA, loyalist paramilitary groups, including the Ulster Volunteer Force (UVF) and the Ulster Defence Association (UDA), who wanted Northern Ireland to remain in the UK, also increased violent campaigns.
30 years of violence ensued, resulting in over 3,600 deaths. Around 1,400 British military personnel died during the deployment and they killed 306 people.
The rest of the fatalities were made up of civilians and paramilitaries.
How was the Good Friday Agreement reached?
After more than a decade of violence, in the early 1980s, the Irish and British Governments began working closer together to find a political settlement that would be acceptable to the whole community in Northern Ireland.
In 1993, the two Governments issued a Joint Declaration, which set out a charter for peace and reconciliation in Ireland.
Talks were made difficult by constant paramilitary action on both sides of the debate, however in 1994 the IRA and Loyalist paramilitaries announced a ceasefire.
In December 1995, an international body was set up by US Senator George Mitchell to independently assess the decommissioning of paramilitary arms.
However, in February 1996, the IRA ended its ceasefire and resumed violence, meaning talks broke down.
Later in 1996 talks resumed between the Irish and British Governments and all the parties elected in Northern Ireland. Sinn Fein was excluded until 1997, when the IRA announced a further ceasefire.
The Good Friday Agreement was agreed on 10 April 1998 and overwhelmingly approved in two referendums in both parts of Ireland in May 1998. It was the first all-Ireland vote since 1918.
A controversial condition of the agreement was the early release of around 500 paramilitary prisoners within two years, even though IRA arms had not yet been destroyed.
Who were the key players in the peace process?
The Good Friday Agreement could not have been reached without the cooperation of several key players who were instrumental in the peace process.
Although dozens of politicians were involved, the main participants are widely regarded as Gerry Adams, Tony Blair, Bertie Ahern, Bill Clinton and George Mitchell.
Gerry Adams, former president of Sinn Fein who had links to the IRA, was extremely influential in the process, famously shaking hands in 1997 with new British Prime Minister Tony Blair.
Tony Blair set a target for peace in Ireland soon after becoming Prime Minister. He was the first PM to meet a Sinn Fein leader since 1921 when he met Gerry Adams.
He negotiated with former Taoiseach (prime minister of Ireland) Bertie Ahern and the other parties to sign up to the Good Friday Agreement.
When signing the agreement he famously declared "A day like today is not a day for soundbites, really. But I feel the hand of history upon our shoulders."
Berie Ahern became Taoiseach in 1997 and worked with the new British PM to bring all parties in Ireland to the negotiation table.
Former US president Bill Clinton, an unlikely contributor to Irish peace, became the first president to visit Northern Ireland. It was Bill Clinton who sent senator George Mitchell who brokered the Good Friday agreement.