House Judiciary Chairman Rep. Jerry Nadler in his floor remarks said the rioters who stormed the Capitol will be brought to justice. Amid accusations from some members of Congress that other members may have abetted rioters, he said accomplices on the floor will also be held accountable.

"We will bring the rioters to justice. Their accomplices in this house will be held responsible," Nadler said. "But today we must focus on the gravest threat first: President Trump."

Rep Adam Schiff, D-Calif., who was the lead impeachment manager for Trump's last impeachment proceedings said America has endured a Civil War, world wars, the Great Depression and now "a Trumpist and white nationalist insurrection," but the nation will prevail because of those Americans patriotic enough restore it.

"This is one of those moments," Schiff said. "Enough."

Rep. James Clyburn, D-S.C., argued that while Republicans are calling for unity and healing, it was the president who refused to recognize Biden's win, leading to a violent transition of power.

"This president's refusal to participate in the peaceful transfer of power and his role in the incitement of last week's violence poses an existential threat. This threat must be extinguished immediately," Clyburn said.

Rep. Jamie Raskin, D-Md., co-sponsor of the impeachment article, warned of future threats to lawmakers if the president isn't held accountable, stressing, "Every one of us in this room right now could have died."

Rep. Jim Jordan, R-Ohio, one of the president's staunchest supporters, began the House debate for Republicans by opposing impeaching Trump and railing against Democrats for what he called their attempt to "cancel the president."

"We should be focused on bringing the nation together. Instead Democrats are going to impeach the president for a second time, one week, one week before he leaves office. Why? Why? Politics and the fact that they want to cancel the president," he said.

"Impeachment round two. It's always been about getting the president, no matter what. It's an obsession. An obsession that's now broadened. It's not just about impeachment anymore. It's about canceling," he added.

Rep. Tom McClintock, R-Calif., told the chamber, "I cannot think of a more petty, vindictive and gratuitous act than to impeach an already defeated president a week before he is to leave office."

"President-elect Biden's promise to heal the nation becomes a hollow mockery in the harsh reality of this unconstitutional act," he said.

Biden and Vice President-elect Kamala Harris have deflected when asked questions about impeachment, saying the decision is with Congress.

After the House Reading Clerk concluded reading the full impeachment resolution against President Trump, the House has proceeded with the session by kicking off two hours of debate on the article on impeachment charging Trump with inciting an insurrection. House Speaker Nancy Pelosi was the first to deliver remarks and called Trump “a clear and present danger” to the country.

"The president of the United States incited this insurrection, this armed rebellion, against our common country. He must go. He is a clear and present danger to the nation that we all love," Pelosi said. "Since the presidential election in November, an election the president lost, he has repeatedly lied about the outcome, sowed self-serving doubt about democracy and unconstitutionally sought to influence state officials to repeal reality."

"My fellow members, my fellow Americans, we cannot escape history. Let us embrace our duty, fulfill our oath, and honor the trust of our nation. And we pray that God will continue to bless America," she added, calling on the House to vote to impeach Trump and for the Senate to vote to convict him.

A spokesperson for Pelosi confirmed to ABC News she is wearing same outfit Wednesday that she wore for Trump's last impeachment vote on Dec. 18, 2019.

-ABC News' Benjamin Siegel

House Reading Clerk Susan Cole, donning an American flag mask, recited the article of impeachment before two horus of debate on the resolution kicked off.

Democrats formally introduced an impeachment resolution Monday, charging Trump with "incitement of insurrection" after he told his supporters at a “Save America Rally” to march on the Capitol during Congress’ joint session to count Electoral College votes on Jan. 6.

"In all this, President Trump gravely endangered the security of the United States and its institutions of Government. He threatened the integrity of the democratic system, interfered with the peaceful transition of power, and imperiled a coequal branch of Government. He thereby betrayed his trust as President, to the manifest injury of the people of the United States," Cole read aloud from the measure.

The impeachment article also cited Trump's call with the Georgia Republican secretary of state where he urged him to "find" enough votes for Trump to win the state -- along with the Constitution's 14th Amendment, noting that it "prohibits any person who has 'engaged in insurrection or rebellion against' the United States" from holding office.

Addressing the coronavirus pandemic, confronting the climate crisis and building public trust in science and technology will be among the Biden administration's key areas of focus, the president-elect said during a press briefing introducing four key members of his science team.

Building back the economy "to ensure prosperity is fully shared all across America" and ensuring the U.S. "leads the world in technologies and industries that the future" will also be a focus, Biden said Saturday during an address in Wilmington, Delaware.

Helping lead those initiatives will be Eric Lander, the presidential science advisor-designate, a position that for the first time will be a cabinet rank, Biden noted.

"I've always said that the Biden-Harris administration will lead with science and truth," Biden said. "We believe in both. This is how we're going to, God willing, overcome the pandemic and build our country back better than it was before. That's why for the first time in history, I'm going to be elevating the presidential science advisor to a Cabinet rank, because we think it's that important."

Frances Arnold and Maria Zuber will be at the helm of the first all-women team to lead the President’s Council of Advisors on Science and Technology.

Alondra Nelson will also be deputy director for science and society for the Office of Science and Technology Policy.

Dr. Francis Collins, who was not present at the event, will also continue in his role as director of the National Institutes of Health.Biden thanked him for "being willing to stay on," saying that it wasn't his original plan.

"I've known Dr. Collins for many years. I worked with him closely," Biden said, accling him "brilliant, a pioneer, a true leader."

"This is the most exciting announcement that I have gotten to make in the entire Cabinet," Biden said of his picks. "These are among the brightest, most dedicated people, not only in the country but the world."