At what age did Twilight's Kristen Stewart begin acting?

When asked about the New Moon sequel, Twilight director Catherine Hardwicke stated,

    It's got werewolves, it's got visual effects that turn people into werewolves, it's got motorcycle stunts, you go to Italy. It's probably twice as much as this [to film]."

Summit Entertainment released a synopsis of New Moon:

    Bella Swan is devastated by the abrupt departure of her vampire love, Edward Cullen, but her spirit is rekindled by her growing friendship with the irresistible Jacob Black. Suddenly she finds herself drawn into the world of the werewolves, ancestral enemies of the vampires, and finds her loyalties tested."

Kristen Stewart, Twilight's Bella Swan co-starring with Robert Pattinson, Nikki Reed...had a career that began at the age of eight, after an agent saw her perform in her elementary school's Christmas play.  Stewart's first role was a short, nonspeaking part in the Disney Channel TV production The Thirteenth Year.

Later Stewart appeared in the independent film The Safety of Objects and Panic Room, playing the sullen, diabetic daughter of a divorced mother (Jodie Foster). The film received generally positive reviews, and Stewart garnered positive notices for her performance.

On working on the film Panic Room (2002) with such a big name star as Jodie Foster:

    When I got Panic Room I`m like, `Oh my God that`s huge! It`s bigger than huge.` I was kind of freaked out at first." - Kristen Stewart (Photo & Quote/QuoteLucy)

After Panic Room's success, Stewart was cast in another thriller, Cold Creek Manor, playing the daughter of Dennis Quaid and Sharon Stone's characters.

In 2005, Stewart appeared in the fantasy-adventure film Zathura, playing the role of Lisa, the irresponsible older sister of two little boys, who turn their house into a spacecraft hurtling uncontrollably in outer space by playing a board game. More films to follow, including In the Land of Women (2007), a romantic drama starring Meg Ryan and Adam Brody.