When does a star become an icon? The moment she passes the six million mark on Twitter? The day she is nominated for six Grammy Awards? Or the month (August 2010) in which it is calculated she has sold more than 15 million albums and 51 million singles worldwide? Lady Gaga (left) has done all these things.
But that's not it. In her own words: "God put me on earth for three reasons: to make loud music, gay videos and cause a damn ruckus." Ah, the ruckus. It has become the Gaga art form, most recently seen in the shape of a dress made of raw meat that she wore to the MTV Video Music Awards, provoking outrage and uproar in equal measure ("What does Lady Gaga's meat dress mean?" asked the BBC).
Gaga is used to such reactions: the world attends her every theatrical move, from the live routine that left her blood-soaked and ailing onstage to the red leather Elizabeth I dress that she wore to meet the Queen at the Royal Variety Show last year. And yet, while some say she redefines empty exhibitionism, her army of obsessed fans - whom she calls her "Little Monsters" - surge to her defence.
This is Gaga's trick. While she is mainstream enough to sell huge quantities of records and duet with Beyoncé (on the nine-minute song "Telephone", whose video features prison bondage and lesbian kisses), she has established herself as an ambassador for the marginalised, the lonely, the misunderstood. It's a lucrative market.
There's a limitless supply of alienated teenagers willing to sign up to a life of Gaga worship, especially since she tattooed her love for them on her arm (near another of her tattoos, from Rilke: "In the deepest hour of the night, confess to yourself that you would die if you were forbidden to write. And look deep into your heart where it spreads its roots, the answer, and ask yourself: must I write?") But she was not always Gaga.
Born in New York City in 1986, Stefani Germanotta went to a private Catholic school on the Upper East Side, although she says her parents were from "lower-class families". She was always, she says, an outsider, but a dorm-mate at New York University remembers her as "a very suburban, preppy, friendly, social party girl".
The name "Lady Gaga" was born of a misspelt text by her then collaborator and producer, Rob Fusari (who tried to sue Gaga, saying she failed to pay him royalties for songs that he had co-written) - yet a New York Post profile claimed it was concocted by music industry executives.
This, too, is Gaga: a myth. The comparison is often made with Madonna - Gaga has inherited her mantle of Catholic-girl-turned-provocatrice. The feminist author Camille Paglia calls it "theft", an image of an icon repurposed for modern times, but Gaga has morphed the brand with her own uncompromising, outlandish, androgynous style.
And for her millions of Little Monsters, she is not just an artist, a singer, or a wearer of impossible clothes, but their champion and heroine: the ultimate "self-professed freak".
Previous: 43. Amartya Sen
Next: 45. Malalai Joya