Biden comes into office during an uncertain time for the country on many fronts -- a raging coronavirus pandemic, months of protests over racial injustice and a bitterly fought election that ended in the siege of the U.S. Capitol just days ago. Biden will be the first president in more than a century not to be greeted by the outgoing president -- Donald Trump is set to depart to his residence in Florida earlier in the day.
Biden's journey from being a son of Scranton, Pennsylvania to the White House has been a long one -- serving as vice president to the first Black president for eight years and then before that, a senator from Delaware for decades. He has faced personal tragedy on a number of occasions but that grief has shaped him.
Here's what to know about him:
Name: Joseph Robinette Biden Jr.
Date of birth: Nov. 20, 1942
Hometown: Scranton, Pennsylvania
Family: Married to Jill Biden, father to Hunter, Ashley and the late Joseph Robinette 'Beau' III and Naomi. Biden's first wife, Neilia, died in a car accident with their baby daughter Naomi in 1972. Beau Biden died in May 2015 of brain cancer.
Education: He graduated from the University of Delaware and Syracuse Law School.
What he used to do: He served as vice president from 2009 to 2017. From 1973 to 2009, Biden served in the U.S. Senate and was on two key committees as both ranking member and chairman: the Senate Foreign Relations Committee and the Senate Judiciary Committee. He also served on the New Castle County Council after finishing law school. Since leaving the White House, Biden and his wife launched the Biden Cancer Initiative to invest in efforts for cancer prevention, detection, diagnosis, research and care.
Key life/career moments:
After publicly supporting same-sex marriage ahead of his boss, Biden reportedly apologized to Obama in 2012. But Obama said in an interview with ABC's “Good Morning America” co-anchor Robin Roberts, "I think Joe is an extremely generous loving person. And I think he was responding honestly in terms of how he felt."
Perhaps one of the most poignant moments of his vice presidency came when Obama surprised Biden with a Presidential Medal of Freedom.
The University of Pennsylvania announced the Penn Biden Center for Diplomacy and Global Engagement to honor his "unsurpassed understanding of diplomacy and far-ranging grasp of world issues" in 2017. That same year, the University of Delaware announced a partnership with Biden to launch the Biden Domestic Policy Institute.
During Biden's Senate career, he oversaw the confirmation of Supreme Court Justice Clarence Thomas in his role as the head of the Judiciary Committee. He was criticized for his handling of the hearing after Anita Hill testified before the committee, and his failure to defend Hill as she faced questioning from an all-white, male committee, as Republican members sought to discredit her testimony.
Biden voted against Thomas, but the Senate nonetheless confirmed the then-nominee. Biden has publicly apologized to Hill, and said in March at the Biden Courage Awards he regrets he "couldn't come up with a way to get (Hill) the kind of hearing she deserved."
Biden has also led the charge on the sweeping, bipartisan 1994 crime bill -- a bill Biden referred to as the "Biden Crime Bill" during his 2008 presidential campaign -- which critics say had a disproportionate impact on minority communities, particularly due to mass incarceration.
Biden undertook three presidential runs during his nearly 50 years in public life, with the first, in 1987, ending before any primary voting took place due to a plagiarism scandal. In that case, Biden quoted British Labor party leader Neil Kinnock without attribution. Biden also faced questions of plagiarism in law school after a paper he wrote did not include proper citation for some of the text.
He admitted to that in 1987, called it a "mistake" and said that there wasn't "malevolent" intent, according to reports at the time.
His second presidential run during the 2008 primary ended after the Iowa Caucuses, where Biden received less than 1% of the vote.
Where he stands on some of the issues:
Biden has expanded his plan for higher education and proposes offering free college tuition for public universities, historically black colleges and universities, and minority-serving institutions to families making less than $125,000, along with his previous pledge to make community college tuition free.
Biden's plan for health care would attempt to make the Affordable Care Act easier to navigate with more choices. His plan would expand upon the Affordable Care Act passed under the Obama-Biden administration and provide a public option for patients to buy into, rather than Sen. Bernie Sanders' "Medicare for All" system that several of Biden's rivals advocated for during the primaries.
Biden has also put a large focus on addressing climate change, calling it one of the four crises facing the country today. In the summer of 2020, he unveiled a sweeping new proposal that called for the United States to achieve a carbon-free power sector by 2035 and a $2 trillion investment over his first four years in office in green energy and infrastructure to combat the threat of climate change.
Biden has also put forth several plans to address the coronavirus pandemic, pledging to follow the science and heed the advice of experts. Biden plans to mandate masks on federal property for the first 100 days of his administration and faces the deep challenge of vaccinating the U.S. population.
In the wake of protests across the country over racial inequality last summer, Biden has not joined the calls to defund police departments, but advocates for providing an additional $300 million in funding for community-based policing, as well as pairing police with mental health experts to be able to better address community needs, while also advocating for a national use-of-force standard.
What you might not know about him:
As a child and teenager, he struggled with a stutter. A young Biden overcame the affliction through public speaking.
During his college years at the University of Delaware, Biden played football.
Biden was first sent to Washington in 1972 when the people of Delaware elected him to the U.S. Senate at 29 years old. He was one of the youngest people elected to a seat in the upper chamber.
In the weeks after being elected to the Senate in 1972, tragedy struck the Biden family after a car accident killed his first wife, Neilia and their 1-year-old daughter, Naomi, and severely injured his sons, Beau and Hunter. In 1977, he married Jill Biden.
After Biden's 46-year old son, Beau, died of brain cancer in 2015, Obama eulogized the former Delaware attorney general during a memorial service. The Biden family received 72,000 condolences through the White House's virtual system after the death of Beau -- and condolences were submitted from every state, according to the vice president's office.
One of Biden's significant achievements during his time at the helm of the Judiciary Committee was appointing California Sen. Dianne Feinstein to the dais. She was the first woman on the committee.
ABC News' Soorin Kim, Sruthi Palaniappan and Christine Szabo contributed to this report.