The new Congress will make history for seating a record number of women and becoming the most racially and ethnically diverse. Republicans will take more seats in the Senate; Democrats will grab control of the House.
"It's a new day in America," tweeted incoming Rep. Ilhan Omar, D-Minn., one of the first two Muslim women to serve in Congress.
Lawmakers will be confronted by a standoff over money and immigration that has shut much of the government and vexed their predecessors.
What to watch on the first day of divided government under President Donald Trump:
HOW CAN I WATCH?
C-SPAN and various broadcast networks are expected to stream or televise the events. Both the House and Senate convene at noon EST.
THE ORDER OF THINGS
There will be prayers and pledges of allegiance.
In the 435-member House, a roll call will begin on the election of speaker. Rep. Nancy Pelosi, D-Calif., is poised to reprise her role in that post, second in line to the presidency. Once the vote is over, Republican Majority Leader Kevin McCarthy, R-Calif., is expected to speak, followed by an address by Pelosi.
The longest-serving member of the House and its dean, 24-term Rep. Don Young, R-Alaska, will swear in Pelosi. She is then expected administer the oath to House members and delegates at the same time.
In the Senate, Vice President Mike Pence will preside over the oath-taking of the 34 members who stood for election on Nov. 6. Republicans gained two seats in that chamber.
Lawmakers will take this oath: "I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God."
She is, some say, feared. And Pelosi is still giving nothing for the U.S. border wall Trump is demanding in exchange for re-opening the government.
Pelosi, 78, seems to have sewn up her return as House speaker, but her comeback depended on her promise to limit her tenure to a maximum of four years. Doing so quelled a rebellion by a stubborn faction of Democrats demanding a new generation of leaders.
She prevailed, wielding skills she will need to manage the roughly 235 Democrats who will comprise the House majority in the new Congress.
Her ascension sets up a clash with Trump.
But where Trump has Twitter and status among his base as a Washington outsider, Pelosi has a network of allies inside and outside Congress — not to mention three decades in the House.
She's been speaker before, the only woman to hold the post, from 2007 into January 2011.
Rep.-elect Rashida Tlaib, D-Mich., will take the oath on a Quran, and not just anyone's. She'll use a 1734 English translation that belonged to Thomas Jefferson.
Tlaib and Omar are the first two Muslim women to serve in Congress. And they're just a few of the signs of change that spring from the Nov. 6 elections. For the first time, two Native American women are headed to the House. Massachusetts and Connecticut will also send black women to Congress as firsts for their states, while Arizona and Tennessee are getting their first female senators.
In all, 127 women — 106 Democrats 21 Republicans — will serve in the 116th Congress, holding nearly 24 percent of all seats, according to the Center for Women and Politics at Rutgers University. In the Senate, 25 women will serve, with 17 of them Democrats and eight Republicans.
The number of House seats held by Republican women will decline by 10, from 23 to 13.
WHAT'S THE SAME?
Being a freshmen is, well, not as glamorous as winning elections. Governing takes different skills than campaigning. And in Congress, seniority matters, a lot.
"I was kind of the mountain where I was," recalled veteran Rep. Gerald Connolly, D-Va., a former chairman of the Fairfax County Board of Supervisors. "You come here and it's a humbling experience. Get in line. It's fascinating that you have an opinion about that, get over there."
Asked in a brief interview about first-term lawmakers having to temper their expectations, Rep.-elect Alexandria Ocasio-Cortez, D-N.Y., said, "That's right. We'll see."
CAN'T THE NEW CONGRESS REOPEN THE GOVERNMENT?
Not without Trump's agreement, and he isn't budging. He wants billions of dollars for a U.S. border wall. Democrats are refusing. Pelosi said outside the White House that there would be rapid passage Thursday of legislation to re-open the government — without funds for the border wall. But the White House has rejected that package, and it's going nowhere in the Senate.
Associated Press writer Alan Fram contributed to this report.