Who's that lady?

Born to a New York Internet entrepreneur and his telecommunications-worker wife; the older of two daughters.Danced around fancy Upper West Side restaurants, using breadsticks as batons.

Learned to play piano by ear at age 4.

Wrote her first piano ballad at 13 and, a year later, played open-mike shows at NYC clubs such as the Bitter End.

Attended the Convent of the Sacred Heart School, an exclusive Catholic school for girls that counts Paris Hilton, Candice Bergen and Gloria Vanderbilt as alumnae.

Starred in "Guys and Dolls" (as burlesque singer Adelaide) and other school musicals.

Enrolled early (at age 17) at New York University's Tisch School of the Arts but dropped out in sophomore year.

Signed with Def Jam Recordings at 19 but was dropped by the label a few months later.

Signed with an imprint of Interscope and Sony/ATV Music Publishing, which led to writing songs for Britney Spears, New Kids on the Block and Pussycat Dolls. Also signed a deal with hit singer Akon.

Released the single "Just Dance" in April 2008. It became a club hit that summer.

Offered the album "The Fame" on Oct. 28, 2008. It went on to sell 12 million worldwide, 3.6 million in the States.

Topped the pop chart with "Just Dance" in January 2009.

Embarked on Fame Monster Tour of clubs, including the Fine Line in Minneapolis in March 2009.

Undertook Monster Ball Tour as she released "The Fame Monster" EP.

Sang for Queen Elizabeth at the 2009 Royal Variety Performance.

Interviewed by Barbara Walters as one of "10 Most Fascinating People of 2009" and glorified her androgyny.

Nominated for six Grammys including record of the year ("Poker Face"); won two trophies in dance categories.

Ranked fourth on Forbes magazine's celebrity power list, behind Oprah, Beyoncé and James Cameron.