Most people don't have a clue what the spiritual movement Kabbalah is, though they may be aware it has something to do with a parade of stars -- from Madonna to Demi Moore and Ashton Kutcher to Britney Spears, Lindsay Lohan and Paris Hilton -- wearing red strings on their wrists.
Kabbalah has become a multimillion-dollar empire with more than 40 branches all over the world. But is the Kabbalah of the stars the same Kabbalah that Jewish men in Israel have been quietly studying for centuries?
In cryptic and mystical terms, Kabbalah explores the nature of God and the universe. Rabbis have traditionally believed the philosophy behind it is so complicated that it could only be taught to ultra-religious Jewish men over 40 who had spent their lives studying Judaism.
In 1971, with virtually no money, Karen Berg and her husband, Philip Berg -- the spiritual leader known to followers as the Rav -- opened their first Kabbalah Centre, turning traditional Jewish wisdom upside down by offering Kabbalah study to women and non-Jews. The Bergs had a simple but radical idea: Kabbalah wasn't just for elite Jewish scholars but was something that could be simplified and taught to everyone.
"It wasn't until we started really bringing it to the people that they actually had access to this knowledge," Karen Berg told Elizabeth Vargas in an exclusive "20/20" interview.
Their movement picked up momentum quickly, Berg said. "It was almost like Jesus ... talks on the Mount and brought people. And they believed in what he said. And they brought more people ... God forbid, I'm not saying that we're messiah consciousness. I'm only saying that we built in the same fashion."
However the Bergs built their movement, many followers say Kabbalah has changed their lives. And the adherents aren't just celebrities.
Don Ellis, a former FBI agent who now practices law and runs a bodyguard service, was raised a Southern Baptist in Texas. He says Kabbalah gave him the spiritual answers he'd been searching for. "I studied a number of different religions, spiritualities, searching for something. And then one day, I saw a CD set called 'Power of Kabbalah.' That's all it took for me was that one series. I haven't looked back since," he told Vargas.
There are no Kabbalah Centres near Ellis' home, so he stays connected by listening to their tapes. He said Kabbalah has created spiritual and financial miracles for him.
The Bergs have brought this ancient wisdom out of the dark ages and mass-marketed it, hawking must-have accessories like red strings and Kabbalah water, which the Centre aggressively sells and claims will protect followers from "negative energy." At services and classes, they teach that Kabbalah is not a religion but a "technology for the soul" that plugs anyone into what they call the "Light" or God -- a God that has 72 names, which if meditated on, can make your dreams come true.
But rabbis like Yitzchok Adlerstein, a professor of law and ethics at Loyola University in Los Angeles, question some of the practices of the Kabbalah newcomers -- like Britney Spears, who tattooed one of God's 72 names in Hebrew on her neck. "Using one of the names of God on her neck is going to bring enough prosperity to Britney as my tattooing Britney's name to my neck. I guarantee you," Adlerstein told "20/20."
"What the Bergs are offering is not remotely Kabbalah," he added.