President Obama was sworn in Sunday to a second term, during a subdued and private White House ceremony that precedes the pomp of Monday's public inauguration.
The president was surrounded by his immediate family and was sworn in by Chief Justice John Roberts on a bible belonging to the family of his wife, first lady Michelle Obama.
The first lady stood to the president's left and held the Robinson family bible as daughters Sasha and Malia stood beside her, inside the White House's Blue Room.
The oath took about two minutes and was administered shortly before noon.
Obama hugged his wife and said, "Thank you Sweetie," after the oath was administered.
He then hugged his daughters and told Sasha, "I did it."
Earlier in the day, Obama joined Vice President Biden, after he was sworn in, at Arlington National Cemetery for a wreath-laying ceremony on a crisp, sun-splashed January day.
Obama and Biden jointly placed a large wreath, adorned with red, white and blue ribbon, in front of Arlington's Tomb of the Unknowns. Placing their hands over their hearts, the two leaders stood solemnly as a bugle played "Taps."
Biden was surrounded by family and friends for his brief swearing-in at the Naval Observatory, his official residence in northwest Washington.
Justice Sonia Sotomayor, appointed by Obama as the first Hispanic to serve on the Supreme Court, administered the oath of office to Biden, who placed his hand on a Bible his family has used since 1893.
"I will support and defend the Constitution of the United States," Biden said as he recited the oath.
Among the 120 guests on hand to witness the vice president's second swearing-in were Attorney General Eric Holder, departing Interior Secretary Ken Salazar and several Democratic lawmakers.
Sunday's subdued ceremonies are a function of the calendar and the Constitution, which says presidents automatically begin their new terms at noon on Jan. 20. Because that date fell this year on a Sunday -- a day on which inaugural ceremonies historically are not held -- organizers scheduled a second, public swearing-in for Monday.
A crowd of up to 800,000 people is expected to gather on the National Mall to witness that event, which will take place on the Capitol's red, white and blue bunting-draped west front. Supreme Court Chief Justice John Roberts, who famously flubbed the oath of office that Obama took in 2009, was to swear the president in both days.
Once the celebrations are over, Obama will plunge into a second-term agenda still dominated by the economy, which slowly churned out of recession during his first four years in office. The president will also try to cement his legacy with sweeping domestic changes, pledging to achieve both an immigration overhaul and stricter gun laws despite opposition from a divided Congress.
But for one weekend at least, Washington was putting politics aside. Obama called the nation's inaugural traditions "a symbol of how our democracy works and how we peacefully transfer power."
"But it should also be an affirmation that we're all in this together," he said Saturday, as he opened a weekend of inaugural activities at a Washington elementary school.
The Blue Room is an oval space with majestic views of the South Lawn and the Washington Monument.
The room, named for the color of the drapes, upholstery and carpet, primarily has been a reception room as well as the site of the only presidential wedding in the White House, when President Grover Cleveland married Frances Folsum in 1886.
Obama and Biden were to address supporters Sunday evening at an inaugural reception.
The president planned to save his most expansive remarks for Monday's inaugural address to the crowd gathered on the Mall and millions more watching across the country and the world. Obama started working on the speech in early December and was still tinkering with it into the weekend, aides said.
The president's address will set the stage for the policy objectives he seeks to achieve in his second term, including speeding up the economic recovery, passing comprehensive immigration and gun control measures and ending the war in Afghanistan. Aides said Obama would save the specifics of those agenda items for his Feb. 12 State of the Union address.
The president launched a weekend of inaugural activities Saturday by heading up a National Day of Service. Along with his family, Obama helped hundreds of volunteers spruce up a Washington area elementary school.
Obama wore rubber gloves, picked up a paint brush and helped volunteers stain a bookshelf.
Obama added the service event to the inaugural schedule in 2009 and is hoping it becomes a tradition followed for future presidents.
Mrs. Obama, speaking to volunteers Sunday, espoused the importance of giving back in the midst of the weekend of pomp, circumstance and celebration.
"The reason why we're here, why we're standing here, why we're able to celebrate this weekend is because a lot of people worked hard and supported us, and we've got a job to do and this is a symbol of the kind of work that we need to be doing the next four years," Michelle Obama said at Burrville Elementary.
The Associated Press contributed to this report.