NEW PHOTO: Oprah Winfrey & Michelle Obama

PHOTO GALLERY: See photos from Time Magazine's 100 Most Influential People Gala

In opening remarks at the gala, Mrs. Obama asked attendees to encourage young people to pursue careers in public service and social innovation.

Others who made Time's list this year include Hillary Clinton, Rush Limbaugh, George Clooney, Tom Hanks, Zac Efron, and rapper M.I.A.

The list was first published in 1999 as a result of a debate among several academics.

In 2007, Time 100 list managing editor Richard Strengel explained that the Time 100 was not a list of the hottest, most popular or most powerful people, but rather the most influential, stating:

"Influence is hard to measure, and what we look for is people whose ideas, whose example, whose talent, whose discoveries transform the world we live in. Influence is less about the hard power of force than the soft power of ideas and example. Yes there are Presidents and dictators who can change the world through fiat, but we're more interested in innovators like Monty Jones, the Sierra Leone scientist who has developed a strain of rice that can save African agriculture. Or heroes like the great chessmaster Garry Kasparov, who is leading the lonely fight for greater democracy in Russia. Or Academy Award winning actor George Clooney who has leveraged his celebrity to bring attention to the tragedy in Darfur."