It has already been a busy week for Obama's Cabinet reshuffle. On Monday, he nominated former Republican Sen. Chuck Hagel to be the next Secretary of Defense and John Brennan, the White House homeland-security and counterterrorism adviser, to be the new director of the Central Intelligence Agency.

Here are some things you need to know about Lew:

1. He was born in New York City, where he got his start in politics.

Lew grew up in a middle-class apartment in Forrest Hills, Queens, where he started taking up causes like building low-income housing, according to The New York Times.

At 12 years of age, he campaigned in New York for Sen. Eugene McCarthy's presidential campaign.