It's the belief system which actor Tom Cruise says has changed his life and made him a better man.
But the controversial Church of Scientology was criticised last week after claims it was preying on people caught up in the London bombings.
Packs of yellow-shirted believers arrived at the scenes of carnage, offering "spiritual healing" to distraught relatives - and £3 booklets titled How To Improve Conditions In Life.
And yesterday 200 "volunteer ministers" were sent out across the capital to talk to people after the latest alerts.
But what exactly is Scientology? A sinister, manipulative cult that claims life on Earth was created by aliens 75 million years ago? Or simply a group of committed believers on a mission to spread their message of peace?
To find out, I enrolled as one. What I discovered disturbed me and raises serious questions about how the church encourages the insecure and vulnerable to boost its growing ranks.
Scientologist Peter presses a book by the movement's founder, L Ron Hubbard, into my hand and says: "This book can change your life."
It is less than five minutes since I walked into the Church of Scientology's headquarters on Tottenham Court Road in London and I'm already feeling under pressure.
Peter tells me how I will achieve more in life because my mind will be cleared of anything negative. He invites me to take a stress test and gives me two metal handles to hold.
At intervals, a needle fluctuates wildly as my stress levels shoot up and Peter asks me what was on my mind. Each time I tell him I'm not sure.
He tells me many people contacted the church after the London bombings and many feel the need for reassurance.
He hands me Hubbard's book on "dianetics" and says it will change my life. I glance inside the thick paperback. It's going to be a difficult week of study.
Most staff are in their early 20s. They offer drinks to passers-by and listen intently to individual worries.
When I tell Peter I'm interested in learning more, he swiftly hands me another book. It highlights the shortcomings of man and the destruction of the natural world, praising Hubbard. Peter warns me that as a volunteer I will have to pay to become qualified.
I tell him I've heard mixed reports about Scientology, but he dismisses my fears, saying: "People always have reservations about something they don't understand."
I'm given a personality test with 200 questions. Some seem geared towards finding a weak spot in my character:
Could you agree to "strict discipline"?
Would the idea of making a complete new start cause you much concern?
Do you sometimes wonder if anyone really cares about you?
Would it take a definite effort on your part to consider the subject of suicide?
Do children irritate you?
Do you often feel depressed?
Do you often ponder over your own inferiority?
Do you have spells of being sad or depressed for no apparent reason?
Back at home, my mind is racing. But I am looking forward to what the results tell me about myself.
It's 9am, and Laura looks at me with pity. She tells me I'm depressed, anxious and nervous. She has analysed the results from my personality test.
But there is a way for me to confront my problems: Scientology. The truth is, I have no worries at present and have never suffered from depression. I would also consider myself outgoing and confident, whereas the test results insist that I'm inhibited and shy.
I'm introduced to a more senior woman called Ann and told she will be able to help me. I'm not asked if I want to be helped - only if I want to set my life straight as it's in disarray.
Within five minutes I'm signing up to a £49.50 Dianetics course - and after a quick lunch break I'm led upstairs to a small classroom.
An African man and an elderly German woman are silently poring over textbooks and filling in answers while a supervisor offers guidance.
I'm taught that the church believes a person is made up of their "thetan", mind and body. The thetan is the person's spirit and never dies - it merely uses the mind and body as a vehicle.
I'm introduced to supervisor Gordon, a short man with glasses. Picture books, wooden building blocks and pebbles are on hand in case I can't understand something.
Studying is from 9am to 6pm, with a lunch break at 12. There is a 15-minute break in the afternoon, and returning late is frowned on. It feels like being back in school, only much stricter.
I'm ushered down into a basement cinema to watch a glossy film about Scientology. Successful people, among them actors John Travolta and Kirstie Alley, tell how it has helped them.
The film seems to blame other religions for the materialism of mankind and the destruction of the planet. It focuses on Hubbard's commercial success and the fortune he made and donated to Scientology. He is even compared with Buddha.
It's recommended I buy seven essential books, as well as DVDs. I reckon saving myself could cost more than £200. I return home exhausted. It's been gruelling.
I'm given the chance to practise "auditing" on an inanimate object. This is an essential technique which helps students to address negative memories, called engrams, that are holding back true potential.
I sit in front of a cardboard box, with a fellow student. I'm judged on my ability to hold a conversation with the box and told off for not directing my gaze at it as I speak.
Then I'm told I'll be taking part in "group processing" with seven other students. They all look as nervous as I feel as a man gives us commands which we are to follow.
He slowly repeats: "Feel your chair. Thank you. Look at the front wall. Thank you. Feel your chair. Thank you. Look at the front wall. Thank you."
For a bizarre hour these are virtually the only words I hear. After half an hour, the man tells us to look at the walls, floor and ceiling and imagine them saying to us: "You have arrived."
We sit in silence for five minutes. Then it begins again - 30 more minutes of nothing except the man repeating: "Feel your chair. Thank you. Look at the front wall. Thank you."
An eerie silence fills the room. Everyone leaves looking slightly stunned. I stumble out feeling dazed and troubled. My head hurts.
I make it clear that I'm not comfortable with the idea of a day of auditing. I'm not sleeping well and I've got a bad headache.
My supervisors aren't too happy and I feel guilty. One member of staff says that it isn't a "good indication".
Instead, I am sent out with some Volunteer Ministers for the day. Quickly, I'm taught how to do a nerve "assist", a touch assist and a location assist - three methods of relieving stress and pain.
These help people achieve calm by allowing "communication waves" to reconnect between the thetan and mind. With that, I'm on my way to the streets of North London with three other VMs - a grandmother and granddaughter from France and a Frenchman called Alen.
We are told we are going to set up "near where all the bombs went off". We set up on the busy Islington Upper Street and soon attract interest. A People walk by and mutter: "It's the aliens" and "Scientology rubbish".
We are encouraged to offer people assists. Once we get them listening, our aim is to take a name, address and phone number.
We are given booklets to offer for a "suggested donation" of £3. We are not to say they are for sale. We provide assists to about 10 people and hand out several hundred leaflets.
I'm whisked into a room and introduced to Mike. He is an experienced auditor and will put me through the process to see how I react.
Mike reassures me that what happens won't harm me in any way, but I feel vulnerable and confused.
I close my eyes as he asks me to regress to a negative incident in my life that I feel comfortable confronting. I'm encouraged to visualise everything around me and put myself back in space and time.
Scientologists believe this will "clear the engram" and I will have no more of the negative memories.
Afterwards I feel shaken, especially when I realise the session lasted one hour and 30 minutes - I'd guessed it was 30 minutes maximum.
It was an experience I won't volunteer for again. I didn't feel in danger at any point but it was deeply unsettling. By 6pm on my final day I am desperate to leave.
I can't believe how quickly I became immersed in the church. I constantly felt the need to accept what I was being told.
It's been an incredibly stressful week. I feel a great wave of relief as I walk out for the last time.
A spokeswoman for the Church of Scientology said yesterday: "Anyone can come into a Scientology church and train on workable solutions for anything from how to repair a broken relationship, how to communicate with others, how to build happy relationships, handling of drug problems, raising children, how to organise and be more efficient at work and many others."
Scientology was founded by sci-fi writer L Ron Hubbard. His book Dianetics: The Modern Science Of Mental Health has sold millions of copies. He died in 1986.
One belief is that 75 million years ago, an alien named Xenu ruled more than 76 planets, including Earth (known as Teegeeack), and tried to solve a population problem by blowing up beings on Teegeeack. Their souls were taken to a "cinema", where they were forced to watch a "3-D, super-colossal motion picture" for 36 days that implanted a "false reality" to control them. These souls then possessed humans.
The Scientologists aim to help people become "clear" to ease crime, mental and physical illness, warfare and drug addiction.
Critics have accused it of being a dangerous cult, mainly concerned with making money.