Yet there's a lot more to this religion than just its ties to Tinseltown. Scientology is probably one of the most successful new American faiths to have emerged in the past century. But despite its success -- and like a lot of other belief systems -- what Scientologists believe and how they perceive a higher power is often misunderstood.
Scientology describes itself as a religion that was founded in the 1950s by L. Ron Hubbard.
At the core of Scientology is a belief that each human has a reactive mind that responds to life's traumas, clouding the analytic mind and keeping us from experiencing reality. Members of the religion submit to a process called auditing to find the sources of this trauma, reliving those experiences in an attempt to neutralize them and reassert the primacy of the analytic mind, working toward a spiritual state called "clear."
The process involves a device called E-meter, which Scientologists say measures the body's electric flow as an auditor asks a series of questions they say reveals sources of trauma.
"Auditing uses processes - exact sets of questions asked or directions given by an auditor to help a person locate areas of spiritual distress, find out things about himself and improve his condition," according to the Church of Scientology's website.
The church goes on to say, "Science is something one does, not something one believes in."
Auditing purports to identify spiritual distress from a person's current life and from past lives. Scientologists believe each person is an immortal being, a force that believers call a thetan.
"You move up the bridge to freedom by working toward being an 'Operating Thetan,' which at the highest level transcends material law," says David Bromley, a professor of religious studies at Virginia Commonwealth University. "You occasionally come across people in Scientology who say they can change the material world with their mind."
Bromley and other scholars say the church promotes the idea of an ancient intergalactic civilization in which millions of beings were destroyed and became what are known as "body thetans," which continue to latch onto humans and cause more trauma.
Advanced Scientologists confront body thetans through more auditing.
Bromley says the church discloses that cosmic history only to more advanced Scientologists. The church's media affairs department did not respond to requests for comment to this story.
In a 2008 CNN interview, church spokesman Tommy Davis was asked whether the basic tenet of the Church of Scientology was to rid the body of space alien parasites.
"Does that sound silly to you?" laughed Davis. "I mean, it's unrecognizable to me. ... People should really come to the church and find out for themselves what it is."
Who was L. Ron Hubbard?
L. Ron Hubbard was the founder of Scientology. Born in Nebraska in 1911, Hubbard was the son of a U.S. Navy officer who circled the globe with his family, according to Scientology expert J. Gordon Melton, a fellow at Baylor University's Institute for Studies in Religion who writes about Scientology on the religion website Patheos.
Hubbard attended the George Washington University in Washington, D.C., but left before graduating to launch a career as a fiction writer, gravitating toward science fiction.
After serving in World War II, Hubbard published a series of articles and then a book on a what he described as a new approach to mental health, which he called Dianetics. His book by the same name quickly became a best-seller.
The success provoked Hubbard to establish a foundation that began to train people in his auditing techniques. In 1954, the first Church of Scientology opened in Los Angeles, with other churches opening soon after. Hubbard died in 1986. The church is now led by David Miscavige.
Why is the church so controversial?
Many groups and individuals have challenged Scientology's legitimacy as a religion.
Scientologists have faced opposition from the medical community over the religion's claims about mental health, from the scientific community over its claims about its E-meters and from other religious groups about its status as a religion.
"It's part therapy, part religion, part UFO group," says Bromley. "It's a mix of things that's unlike any other religious group out there."
For a long time, the Internal Revenue Service denied the Scientologists' attempts to be declared a church with tax-exempt status. But the IRS granted them that status in 1993.
Many members say the church is largely about self-improvement.
"What I believe in my own life is that it's a search for how I can do things better, whether it's being a better man or a better father or finding ways for myself to improve," Tom Cruise told Playboy magazine
. "Individuals have to decide what is true and real for them."
What does Scientology teach about psychiatry?
L. Ron Hubbard rejected psychiatry and psychiatric drugs because he said they interfered with the functioning of the rational mind. Scientologists continue to promote that idea.
The Church of Scientology's website
says that "the effects of medical and psychiatric drugs, whether painkillers, tranquilizers or 'antidepressants,' are as disastrous" as illicit drugs.
How many Scientologists are there?
That's a matter of considerable dispute.
The Church of Scientology says it has 10,000 churches, missions and groups operating in 167 countries, with 4.4 million more people signing up every year.
Scholars say that, despite the global proliferation of church buildings, the membership numbers are much lower than the church claims, likely in the hundreds of thousands. Several of the church's followers are Hollywood celebrities.