Two days from now, Donald Trump and his wife, Melania, will arrive at the White House for morning tea with President Barack Obama and his wife, Michelle. Upstairs, in the residence, movers will rush around, simultaneously packing up the outgoing family's last belongings as they unload those of the Trumps.
By lunchtime, Obama will have handed over the reins of the world's most powerful nation to a man who vowed to tear down his biggest achievements and who defeated Obama's chosen successor. A military aide with a briefcase holding the US nuclear launch codes will stop trailing Obama and leave the US Capitol in Trump's entourage.
After a rancorous campaign that blew away precedent, an election result that shocked the political establishment and a transition by Twitter that upended convention, the unorthodox will be overtaken - at least for a few hours - by tradition.
The inauguration is "one of those great turning points" in the nation's political consciousness, historian William Seale said. "Everything was going along one way and suddenly there's a turnaround, and he won. A stop and a change. A re-evaluation." Trump's swearing-in will be "the moment on the head of a pin", he said.
One of the most intriguing aspects of the day will be the limousine ride that Obama and Trump will share on the ride to the Capitol past thousands of onlookers. It promises to be especially awkward: Trump, the real estate magnate and reality-TV star who never held political office, spent years stoking false doubts about Obama's legitimacy to hold office. Obama spent months telling voters that Trump was uniquely unqualified to be president, declaring that it would be a personal insult were he elected.
"His instruction to me was, 'The campaign is over, I am now president for all the people'," Tom Barrack, the chairman of Trump's inaugural committee, said this week.
Barrack, the chairman of Colony Capital, said that the Republican wants to "heal the wounds" of the election, to reach out to Americans with questions and doubts and "build a bridge and tie them back in".
Some Democratic members of Congress, including African-American civil rights icon John Lewis, have said they are boycotting the ceremony. In a Twitter post on Saturday, Trump criticised Lewis, who suffered a cracked skull while fighting for voting rights in the 1960s, as "all talk", a day after the Georgia congressman said he doesn't consider him "a legitimate president".
Law enforcement officials expect between 700,000 and 900,000 people to attend inauguration events, about half the 1.8 million the Washington D.C. local government estimated were at Obama's first inauguration.
About 100 different organisations are planning demonstrations either for or against Trump, Homeland Security Secretary Jeh Johnson said.
Much of downtown Washington will be closed to traffic to maintain tight security for the occasion.
About 28,000 personnel will be dedicated to security.
In a nod to the heavily rural constituency that helped propel Trump to the presidency, country singers Toby Keith and Lee Greenwood will be featured performers along with military bands at a "Make America Great Again!" event on the steps of the Lincoln Memorial the evening before the inauguration, the inaugural committee announced.
Trump will address the crowd at the concert.
The inauguration itself will reflect Trump's background in reality television. Jackie Evancho, a teenager featured on America's Got Talent, is to sing the national anthem.
Trump is seeking a "delicate balance between abiding by tradition" and leaving "his own fingerprint on a fresh canvas", Barrack said, but added, "Mostly he's abiding by tradition especially in the swearing-in ceremony."
That tradition includes having the chief justice of the US, John Roberts Jr., administering the oath of office to Trump; Vice-President-elect Mike Pence has chosen Justice Clarence Thomas for his swearing-in. Trump will parade down Pennsylvania Ave, past a flashy new hotel that bears his name, back to the White House, to rest up and get changed for the evening's inaugural balls. He may use his presidential authority to issue executive actions even before the night-time balls - as Obama did eight years ago.
Trump plans to issue some executive orders on inauguration day and may swear in some of his Cabinet members, incoming White House press secretary Sean Spicer said yesterday. But the incoming president will wait until Monday, the first full business day of his presidency, for "a big flurry of activity".
When Obama was inaugurated, he and first lady Michelle Obama left the armoured presidential limousine and walked a stretch of the parade route. Trump's team hasn't said yet whether he will do the same.
There is always the potential for drama. Since the early days of the republic, the transfer of power often has been an awkward hand-off. President Dwight Eisenhower thought President John Kennedy too young and inexperienced for the job, and Kennedy's wife Jackie hated that the Eisenhowers let them know it. Rosalynn Carter and Nancy Reagan didn't talk in the motorcade limo they shared on Inauguration Day.
While most of focus will be on the Trumps' arrival, the Obamas will have their own emotional experience, said Kate Andersen Brower, a former Bloomberg News reporter and author of First Women: The Grace and Power of America's Modern First Ladies. On their last morning at the White House, the outgoing first family traditionally gathers the residence staff, about 100 people, in the State Dining Room to say goodbye.
After the swearing-in ceremony, the Obamas will lift off from the Capitol grounds one last time in the presidential helicopter, heading for Joint Base Andrews.
At Andrews, he'll board a presidential aircraft, though it will no longer carry the designation Air Force One. The commander-in-chief won't be aboard.