She was a Harvard professor with courses on administrative law, constitutional law, civil procedure and issues involving the separation of powers until becoming dean in 2003. She was nominated to the Harvard dean position by Larry Summers, then Harvard president and now chief Obama economic adviser. She served in the Clinton White House's Domestic Policy Council.
She and Obama both taught at University of Chicago law school. She attended Princeton and Oxford and, like Obama, received her law degree from Harvard. She also was one of the editors of the Harvard Law Review.
In March 2009 Kagan was confirmed by the senate on a 61-31 vote. Seven Republicans voted in favor of her nomination, joining all of the Democrats. (Sen. Arlen Specter - then a Republican - was among Kagan's opponents.) Her nomination to the D.C. Circuit Court of Appeals by President Clinton in 1999 was blocked by Republicans.
Kagan has been a target of progressives since her name first surfaced as a contender last spring, and the White House issued an unusual defense against some unflattering articles about her record on diversity.
The White House has said they want to see Obama's nominee confirmed by the end of the summer to be in place for the next court session. Kagan was chosen over three other finalists: D.C. Circuit Appeals Court Judge Merrick Garland, Ninth Circuit Court of Appeals Judge Judge Sidney Thomas and Seventh Circuit Court of Appeals Judge Diane Wood, a favorite of progressives. Also on the longish short list were Homeland Security Secretary Janet Napolitano, the former Arizona governor, Gov. Jennifer Granholm (D-MI), Leah Ward Sears, formerly chief justice of the Georgia Supreme Court and Seventh Circuit Court of of Appeals Judge Ann Claire Williams.
Read more about Kagan's background here.