Beyoncé delivered a show-stopping finale to the US presidential inauguration, ripping out her earpiece as she belted out the national anthem after Barack Obama was sworn in for a second term.
The 31-year-old pop star, a major supporter of President Obama, and husband Jay-Z were among a number of celebrities bringing a touch of Hollywood to the ceremony in Washington overnight.
James Taylor was the first to perform, strumming his guitar to a rendition of "America the Beautiful", before Kelly Clarkson took centre stage to sing "My Country "Tis of Thee".
Pop star Katy Perry and musician boyfriend John Mayer sat together in the audience while actress Eva Longoria sat on a platform outside the Capitol, News Day reports.
Beyoncé's performance, accompanied by the US Marine Band, capped off the night.
It was not the first time she sang for President Obama - she also delivered an emotional performance of Etta James' "At Last" at his 2009.
Moments after taking the oath of office and launching into his second term, President Obama declared a decade of war was ending, the US economy was recovering and "America's possibilities are limitless".
"My fellow Americans, we are made for this moment, and we will seize it, so long as we seize it together," Obama said before a flag-waving crowd of hundreds of thousands.
Trumpets blew fanfare and cannons fired as the country watched the president take the oath of office as the world's most powerful elected leader.
Obama's address touched on the broad gifts that brought the country together, and pointed to the work ahead, "the realities of our time".
"We must make the hard choices to reduce the cost of health care and the size of our deficit," he said. "But we reject the belief that America must choose between caring for the generation that built this country and investing in the generation that will build its future."
While he was officially sworn in on Sunday (Monday AEDT), as required by law, the glitter of Inauguration Day - the parade down Pennsylvania Avenue toward the White House, the night of balls, the ceremonial beginning of a new four-year presidential term - still enlivened staid Washington.
The celebration was pushed to Monday (Tuesday AEDT) because January 20 fell on a Sunday this year. That placed the grand ceremony on the US public holiday marking the birthday of revered civil rights leader Martin Luther King.
Obama, the politician who rose improbably from a history as a community organiser in Chicago and a professor of constitutional law to the pinnacle of power, faces a nation riven by partisan disunity, a still-weak economy and an array of challenges abroad.
The president also faces a less charmed standing on the world stage, where expectations for him had been so high four years ago that he was given the Nobel Peace Prize just months into his presidency. "Only very rarely has a person to the same extent as Obama captured the world's attention and given its people hope for a better future," the Nobel announcement in 2009 read.
The president, First Lady Michelle Obama and daughters Sasha and Malia began the day at St John's Episcopal church, which is known as the church of presidents. Obama later had coffee at the White House with congressional leaders, who play major roles in how the country is governed.
The inauguration events had less of the effervescence of four years ago, when the 1.8 million people packed into central Washington knew they were witnessing history. Obama is now older, greyer and more entrenched in the politics he once tried rise above. Officials said crowds were about half what they were four years ago.