Transcript for Dr. Ruth on becoming a sex expert, LGBT ally, American icon
We spent some time on Dr. Ruth's couch. For the record, it was only to interview her. Reporter: You wanted to show me this, sex for dummies. Dr. Ruth can still talk about sex, morning noon and night. I can look at people and tell if they've had good sex or not. Reporter: With her distingtive accent. Let's agree to disagree and let's have good, terrific sex. Reporter: And dim menutive frame, she is a pioneer. And then let him insert his penis into the vagina from behind. Reporter: The 91-year-old has been America's most famous and trusted sex therapist for generations. I would like us all together to bury right here is with the withdrawal method is a method of contraception. Reporter: What makes you so comfortable talking about sex? First of all, I'm very jewish. And in the jewish tradition, it says sex is never sin, it's the tradition of a husband once a week. Tell all your viewers that make-believe tonight is Friday night. Reporter: The life story is a documentary on hulu. "Ask Dr. Ruth". Before I started to do television, the most important thing for me was education. Reporter: An in-depth look at the woman who's talked openly about sex for decades. In the early '80s, people did not talk about sexuality. Reporter: It all began with her radio show, "Sexually speaking"? I do hope that you do mass ter bait, that you bring yourself to sexual satisfaction. Reporter: Did you realize how groundbreaking what you were doing was? I did realize nobody talked about orgasm or ejaculation. I did not realize how successful the radio program was. It's good I didn't realize. Maybe I would have opinion more up tight if I had known that everybody listened to me, Sunday nights from 10:00 to 12:00. I say don't just engage. Reporter: Her willingness to talk publicly about what many had limited to private pillow talk launched her into the mainstream. I've never heard women tell the truth about sex before in public in my life. Reporter: Hosting a string of popular TV shows like "The Dr. Ruth show." You have changed sex. It's not the same thing. Don't tell me it's less good. No, it's like a sport. People suit up for the game. Reporter: The name Dr. Ruth became synonymous with sex. We have to continue to talk about issues of sexuality and issues of sexual transmitted diseases. Reporter: She was one of the first people to use her platform to address the AIDS epidemic. It was a very unpopular topic, because gay people at the time, not only were they minority, but they were despised. Reporter: She refused to stigmatize people with AIDS and instead tried to educate her viewers about HIV and homosexuality. Some people are attracted to members of their own sex, and I believe strongly that we as a society have to give these people all the respect. It seems the high proportion of people who are dying and succumbing to the AIDS virus are still in the homosexual community, intravenus drug users. I don't waste a moment of my time to blame one or another group. I say let's educate, and let's find a cure. Reporter: Her empathy for those suffering during the AIDS crisis was rooted in her own past. I took that very seriously, because of my background as a German, jewish refugee. I certainly had sensitivity for the people who really were regarded as sub human. Reporter: Born in Germany in 1928, her parent tered Switzerland when she was 10 years old after they realized how dangerous Germany had become for Jews. I do have the letters of my parents. Until 1942, when they stopped. Then I knew something terrible must have happened. Reporter: Years later, she returned to Israel to learn her parents' fate. Died in auschwitz, 1942. Oh, boy. My mother's maiden name was hannover. Irma. Irma was murdered in the holocaust, but it doesn't have a specific location. Oh, boy. Sad. Reporter: With all the loss that you've experienced in your life, what makes you so resilient? My whole family were killed by the Nazis. So I had an obligation to make a dent, because 1.5 million jewish children were killed, and I was safe because I was in Switzerland. Despite the fact that I had tragic happenings of be being an orphan at the age of 10 1/2, never seeing my family again, despite that fact, I made a dent in society. At 90, still talking about sex. Reporter: Despite all her fame, she's remained in the same place, right here in this upper Manhattan apartment for 50 years, raising her two children here. You can see the George Washington bridge. Reporter: So look at all these awards you have here. Hall of fame. With all she has accomplished, she says it's life itself that's been the greatest gift. The thing you're most proud of? Yes. Four grandchildren. Hitler's dead and my grand children are alive, and I'm very successful. Reporter: For "Nightline," I'm linsey Davis in New York. Ask Dr. Ruth is streaming on hulu now.
This transcript has been automatically generated and may not be 100% accurate.