Sinn Fein's Michelle O'Neill has made history by being appointed Northern Ireland's first nationalist first minister, with US president Joe Biden commending the region's political leaders.
A power-sharing government has returned as politicians gathered at Stormont to appoint a series of ministers to the devolved executive, two years after it collapsed over the UK government's deal with the EU.
The Democratic Unionist Party's (DUP) Emma Little-Pengelly will serve as deputy first minister.
Under the Good Friday Agreement, the deputy has an authority equal to that of the first minister.
In her speech, which began in Irish, Ms O'Neill said: "Today opens the door to the future - a shared future.
"I am honoured to stand here as first minister."
Ms O'Neill said she was addressing an "assembly for all - Catholic, Protestant and dissenter" and that the public was "relying" on the members of Northern Ireland's elected assembly.
She added: "We must make power sharing work because collectively, we are charged with leading and delivering for all our people, for every community."
Ms O'Neill continued: "As an Irish republican I pledge co-operation and genuine honest effort with those colleagues who are British, of a unionist tradition and who cherish the union... Despite our different outlooks and views on the future constitutional position, the public rightly demands that we co-operate, deliver and work together."
The first minister also acknowledged that the power-sharing coalition will "undoubtedly face great challenges" but vowed to "serve everyone equally".
Ms O'Neill also reflected on the historic significance of her appointment and said: "For the first time ever, a nationalist takes up the position of first minister.
"That such a day would ever come would have been unimaginable to my parents and grandparents' generation."
She added: "This place we call home, this place we love, North of Ireland or Northern Ireland, where you can be British, Irish, both or none is a changing portrait.
"Yesterday is gone. My appointment reflects that change."
Ms O'Neill also spoke about the impact of the UK government's austerity measures on Northern Ireland, telling the assembly the country "cannot continue to be hamstrung by Tories in London".
She added: "Tory austerity has badly damaged our public services. They have presided over more than a decade of shame. They have caused real suffering.
"I wish to lead an executive which has the freedom to make our own policy and spending choices."
Ms Little-Pengelly then gave her speech, in which she recalled witnessing the "absolute devastation" from an IRA bomb.
She said: "Michelle O'Neill and I come from very different backgrounds.
"Regardless of that, for my part, I will work tirelessly to ensure that we can deliver for everyone in Northern Ireland."
She continued: "As a young girl sitting in Markethill High School almost 30 years ago, I could never have imagined that one day I would have the opportunity to serve in such a way.
"This is a responsibility and an honour that I will never take for granted."
She continued: "Like so many across this chamber and throughout Northern Ireland, I grew up with conflict.
"As a child of just 11, I stepped outside my Markethill home on a warm August afternoon to the absolute devastation from an IRA bomb.
"Seared within my experience is the haunting wail of alarms and our emergency services, the carpet of glass and debris, the shock, the crying and the panic that shook and destroyed the place I called home.
"As a child, I didn't understand the politics of it - but I will never forget the fear, the hurt, the anger."
Ms Little-Pengelly also said the "horror" of the Troubles can never be forgotten but said "while we are shaped by the past, we are not defined by it".
Earlier, former DUP leader Edwin Poots was chosen by members of the assembly as its new speaker.
His party had refused to participate in government at Stormont, arguing that post-Brexit arrangements effectively left a trade border in the Irish Sea between Northern Ireland and the rest of the UK.
An agreement a year ago between the UK and the EU, known as the Windsor Framework, eased customs checks and other hurdles but didn't go far enough for the DUP, which continued its boycott.
However, the DUP has since forged a deal with the UK government on post-Brexit trade, which party leader Sir Jeffrey Donaldson says has effectively removed the so-called Irish Sea trading border.
Sir Jeffrey's role as party leader and his resignation from the Northern Ireland Assembly in 2022 means he was ineligible to be deputy first minister.
Ms O'Neill said in her speech after being appointed first minister: "We will now begin to seize the considerable opportunities created by the Windsor Framework.
"To use dual market access to grow our exports and attract higher-quality FDI.
"The Windsor Framework also protects the thriving all-Ireland economy, and we must fully realise its huge potential."
Ms O'Neill's selection as first minister, made possible after she led Sinn Fein to victory in the 2022 Assembly elections, marks the first time the post has been held by a nationalist committed to seeing Northern Ireland and the Republic of Ireland united as one country.
US President Joe Biden said on Saturday evening he strongly supported the Assembly's restoration and commended Northern Ireland's political leaders.
"As I said when I visited Belfast last year to mark the 25th anniversary of the Belfast/Good Friday Agreement, the democratic institutions it established remain critical for the future of Northern Ireland, and a government that finds ways through hard problems together will draw even greater opportunity to Northern Ireland," he said.
"I look forward to seeing the renewed stability of a power-sharing government that strengthens the peace dividend, restores public services, and continues building on the immense progress of the last decades."
"I am confident that... Stormont's restoration will facilitate the critical North-South and East-West relations vital to the Belfast/Good Friday Agreement, and ensure that Northern Ireland will continue to be vibrant and dynamic, defined by unlimited opportunity for all who call it home."