Terry Gross

He plays Niles Krane on Frasier, a role for which he won an Emmy. Pierce has also appeared in many films, including Bright Lights, Big City, Little Man Tate, The Fisher King, Crossing Delancy, Sleepless in Seattle and Nixon. He was recently the voice of Abe Sapien in Hellboy.

NBC's Frasier has its season finale on Tuesday. The character originated on another hit show, Cheers. Grammer got his start in classical theatre, but he's best known for his comic gifts.

As the show winds down, Lloyd discusses the popular sitcom. The show debuted in 1993 and won many awards, including a Peabody.

Underhill studies and tracks the habits of shoppers in order to learn the best way to lead them to make purchases. His retail consulting firm, Envirosell, has helped big-name companies such as McDonald's, Levi Strauss and Blockbuster to study their customers' browsing and buying habits. He's the author of the book Why We Buy, and the new book Call of the Mall.

The demand for oil increases each year, but the supply is not inexhaustible. Experts predict that within 30 years our oil energy sources will be depleted. In his book, The End of Oil: On the Edge of a Perilous New World, Roberts looks at the implications for the world in terms of the economy, politics and the environment, and what alternatives exist for oil. Roberts writes about the energy industry for Harper's magazine and for other national publications.

Carley is the executive director of GRASP, The Global and Regional Asperger Syndrome Partnership. In 2000, he and his then 4-year-old son were diagnosed with Asperger's Syndrome. GRASP works to educate the public about the disorder.

Volkmar is a leading researcher in Asperger's Syndrome, generally considered to be a form of autism characterized by deficits in social interaction and non-verbal communication. In the early 1990s, Volkmar led the team that helped develop the definition of autism used by the American Psychiatric Assoc. He is the Irving B. Harris Professor of Child Psychiatry, Pediatrics and Psychology at the Yale University Child Study Center.

Edwards, former host of NPR's Morning Edition, was reassigned just last week and is now a senior correspondent for NPR. He is the author of the new book Edward R. Murrow and the Birth of Broadcast Journalism. Edwards is also the author of Fridays with Red, about his radio friendship with legendary sportscaster Red Barber.

While The Washington Post's bureau chief in West Africa in 2001, Douglas Farah discovered al-Qaeda's diamond smuggling operations there. His coverage for the Post angered his hosts in West Africa and embarrassed U.S. intelligence officials. Forced to leave Africa and to defend his findings back in the United States, Farah continued his investigation. He's just published a book, Blood from Stones: The Secret Financial Network of Terror, that details his findings.

Her book Eats, Shoots & Leaves, a best seller in Britain, is a narrative history of punctuation. Truss claims that with the advent of e-mail and text messaging, proper punctuation is an endangered species. Truss is also the author of three novels and numerous radio comedy dramas. She has been a television critic and sports columnist for The Times (London). She also won Columnist of the Year award for her work for Women's Journal. She now reviews books for the Sunday Times of London.