As the multimedia pioneer and TV icon celebrates her 59th birthday today, many remember the landmark moments of her career. Most recently, she sat down with cyclist Lance Armstrong, who admitted to using performance enhancing drugs. That interview had a reported 28 million viewers, and is expected to help boost OWN's ratings in the coming quarter. Winfrey has sat down with the who's who of politics, entertainment, and media, and is undeniably a hero in her own right, having been a philanthropist, film and TV producer, and major cultural and business influencer. Take a look at landmark moments from her career, as she continues many more years of expanding her empire: Gabby's Golden Glory Winfrey sat down with Olympic gold medalist Gabby Douglas in August 2012 to talk her journey into gymnastics, racism and bullying she encountered and how her mother and second family played a role in pushing her toward success. Cyclist Scorned: Lance Armstrong After being stripped of his Tour de France titles, cyclist Lance Armstrong sat down for an exclusive interview with Winfrey in which he admitted to using performance-enhancing drugs. The athlete has faced major public scrutiny and disgrace, with many comparing his scandal with that of track star Marion Jones, who served prison time after her October 2007 admission that she took the drugs and lied about it to a grand jury. Remembering Whitney It's been almost a year since the death of pop music icon Whitney Houston, and a little more than a year since Winfrey's final sit-down with the star in January 2009, where Houston talked candidly about her battle with drug addiction, her relationship with ex-husband Bobby Brown and her career comeback. On the Jan. 28, Oprah interviewed Whitney's mother, Cissy Houston, in her New Jersey home, for the first in-depth interview since her daughter's passing. Oh, Obamas! Winfrey first called then Sen. Barack Obama "her favorite" in 2006. She then made a pioneering statement, endorsing his bid for president in 2008. And made history again having a sitting president and his wife, Michelle Obama, on the show for the first time, in one of her final episodes. Beiber Fever Citing her interview with entertainment phenom Justin Beiber as "the biggest thing she's done since her landmark interview with Michael Jackson in 1993," Winfrey chatted with him about about his rise to fame, how it feels to be a young pop icon in the making and his high-profile relationship with actress Selena Gomez. 'Master' of Hip-Hop, Jay Z Having received quite a bit of backlash for being critical of hip-hop culture but never having anyone from the industry welcomed on her couch, Winfrey changed the game by having hip-hop mogul Jay Z on "Oprah's Master Class" where he talked about his rise from Brooklyn's Marcy Projects to music industry artist and entrepreneur to C-suite executive. Kardashian Kraze In June 2012, Winfrey sat down with the most publicized ---and scrutinized--- reality TV family, the Kardashians, where the family discussed the price of uber-accessibility and international fame, Kim's short-lived marriage to basketball star Kris Humphreys , and their tight-knit loyalty and openness despite public criticism. Family matriarch Kris Jenner also revealed her biggest regret and discussed her marriage to Olympic legend Bruce Jenner. Getting Real with Rihanna Multiplatinum superstar Rihanna took Winfrey to her Barbados home, where she gave an exclusive interview on the price of fame, the passing of her beloved GranGranDolly, and her unwavering love for ex-beau, entertainer Chris Brown, who was convicted of felony after physically assaulting the singer in 2009.