Summer Glau is best known for her roles in science-fiction television series. None of them have made it to the 100-episode mark, the benchmark for success in American television, but her performances have made her popular with fans of the genre.
She got her first big break in "Firefly," a 2002-03 sci-fi/Western series about the colonization of multiple Earth-like planets in the twenty-sixth century after Earth itself is uninhabitable. She played psychic child prodigy named River Tam. She later appeared in "The 4400," a series about 4,400 individuals who mysteriously disappear and return decades later, without having aged and remembering nothing about or during their absence. In "The 4400" - which ran for four seasons for, I kid you not, 44 episodes (one episode for each group of a hundred people, apparently) - Ms. Glau played Tess Doerner, a paranoid schizophrenic in a psychiatric hospital who uses a form of mind control to get the patients, doctors and nurses at the hospital to build an unknown structure (sort of like Richard Dreyfuss build a Devil's Tower model in Close Encounters of the Third Kind).
Ms. Glau is probably best known for her role in the 2008-09 series "Terminator: The Sarah Connor Chronicles." She played Cameron Phillips, a cyborg sent back to protect protagonists John and Sarah Connor from an artificial general intelligence system. She also played the cyborg's human doppelgänger, Allison Young. She remains a favorite guest at comic-book and sci-fi conventions.
Fun fact: Summer Glau studied ballet as a girl, and not only did she employ her dancing talents on "Terminator: The Sarah Connor Chronicles." she played a prima ballerina in her first television appearance - on a 2002 episode of"Angel."