"Surveying Sex in the Twentieth Century."

William Masters and Virginia Johnson became famous in the 1960s for their research into the physiology of human sexuality. In Masters of Sex, biographer Thomas Maier explores the duo's research methods, which for years remained shrouded in secrecy.

Sexologist Leonore Tiefer has written a new book called "Sex Is Not a Natural Act: and Other Essays." She looks at our society's anxieties towards and ignorance about sex. She also questions what is "normal" sex. Tiefer received a Ph.D. in physiological psychology, and later specialized in clinical psychology to become a sex researcher, sex therapist and an Associate Professor at the Montefoire Medical Center in New York City. Tiefer has also been a sex columnist for the New York Daily News.

It's estimated that one in 10 women experience endometriosis during their reproductive years, a condition where cells that line the uterus go rogue by moving to other organs, taking root and spreading there, leading to terrible pain. Many women who have the disorder struggle to be properly diagnosed. Bioengineer LINDA GRIFFITH talks about her groundbreaking research into endometriosis.