Actress Leah Remini, best known for her role as Carrie Heffernan on the TV series "The King of Queens," sat down for an exclusive interview with ABC News' "20/20," to talk about her 30 years inside the Church of Scientology, her ultimate decision to sever ties with the Church and her new memoir, "Troublemaker: Surviving Hollywood and Scientology." Watch the full interview on "20/20," Friday, Oct. 30 at 10 p.m. ET.

Prominent Scientologist Tom Cruise joined the Church of Scientology not long after his father died in 1984. Cruise opened up about his beliefs in a 2006 interview with ABC News' Diane Sawyer saying, "[Scientology gives people] tools to help better your life. That's what Scientology is. It helps you to improve your life. "

John Travolta credited Scientology with saving his life and helping him save the lives of others in a 2015 interview with ABC News' Amy Robach. "Forty years for me, I've been part -- and I've loved every minute of it, and my family has done so well with it," said Travolta. "It's a beautiful thing for me and I've saved lives with it. Saved my own life several times." Travolta produced and starred in the film, "Battlefield Earth," which is based on a sci-fi novel by Scientology founder by L. Ron Hubbard.

Jenna Elfman of "Dharma and Greg" fame said in a January 2005 issue of Scientology's magazine, Celebrity, "I intend to make Scientology as accessible to as many people as I can." At the time, she said it's her "duty to clear the planet," by helping people get rid of negative thoughts and emotions. Elfman also appeared at the ribbon cutting ceremony at the opening of the Church of Scientology and Celebrity Centre Nashville in April 2009.

"The basic thing that I think Scientology helps people with is to rehabilitate their own spirit, their own nature, their own personality that was sort of buried or lost somewhere along the way," Kirstie Alley told ABC News in 1998. More recently, Alley told Howard Stern on his SiriusXM radio show in January 2015 that she had reached the OT-7 level in the Church of Scientology's hierarchy of achievements. "It means that you have gotten rid of all the things that would create aberrated behavior in you that you didn't want."

Actor Giovanni Ribisi, who appeared in the movies "Ted" and "Avatar," grew up with Scientology. "I was born into Scientology," Ribisi said in a June 2014 episode of the radio podcast, "WTF with Marc Maron." "There's a lot of people who ask me about Scientology, and at the end of the day, Scientology is a personal thing. And the way I personally view it is as a pragmatic philosophy, meaning that it's not necessarily a set of beliefs that you go around and try to invest belief into, and hope, it's really something that's sort of day-to-day and practical."

Actress Juliette Lewis told Vanity Fair in December 2010 that she was a practicing Scientologist and Christian. When asked by Time Magazine in March 2015 if there were misconceptions about her religion Scientology, Lewis said, "I only ever say, when I'm asked about this-my freedom." She added, "At the end of the day, I'm into protecting my freedom of choice, freedom of voice, freedom of religion, freedom of expression. And so as long as nothing is inhibiting that? But there are misconceptions that are annoying."

Actress Erika Christensen named Scientology as one of the things that help her stay grounded in Hollywood while appearing on the web show hosted by her "Parenthood" co-star Joy Bryant. "It's a huge part of my life because it's a study. It's an applied philosophy," Christensen said in the interview for Reserve Channel in 2013. "If I had to sum it all up, like, the goal of Scientology is giving the person back to themselves, like your own power of choice.

Actress Catherine Bell poses for photos during the 38th Anniversary Gala held at the Church of Scientology Celebrity Centre International, during August 2007, in Los Angeles.

Elizabeth Moss, known as Peggy Olson on AMC's "Mad Men" praised Scientology in a 2013 interview with ABC News' Peter Travers. Moss said Scientology gives her stability and makes her feel like a better version of herself. "I think that's a good way of saying it, because there is so much focus on the, I guess, empowerment and, sort of, respecting yourself, and yourself as an individual," said Moss.

Danny Masterson spoke extensively about his beliefs in a February 2015 interview with Paper Magazine. "In Scientology, there's no belief system or anyone who's worshipped or whatnot; it's all sort of like college of the mind. And so I grew up not having to go and pray to anyone," Masterson said.

"I've been a Scientologist since 1999 and I've never come across any piece of information that remotely is negative or derogatory in any way towards the LGBT community," "Orange Is the New Black" actress Laura Prepon said in a June 2014 interview with Fusion's Alicia Menendez.