A US senator from California the past four years, Harris has shattered many a glass ceiling. She served as San Francisco's first female district attorney and was California's first woman of colour to be elected attorney general.
She was sworn in by US Supreme Court Justice Sonia Sotomayor, the court's first Latina member.
Looking ahead, Harris, 56, is seen as an obvious contender for the Democratic Party's 2024 presidential nomination should Biden, 78, decide not to seek a second term. Harris has yet to weigh in publicly on such speculation.
Harris has resigned her Senate seat, but she still will play a prominent role in the chamber. The US vice president serves as Senate president, casting any tie-breaking votes in the 100-member chamber. With it split evenly between Democrats and Republicans, Harris gives her party control of the Senate.
Her background in criminal justice could help the new Biden administration tackle the issues of racial equality and policing after the country was swept by protests last year. She is expected to be a top adviser on judicial nominations.
Harris is the daughter of immigrants, with her mother coming to the United States from India and her father from Jamaica.