When Brian and Bobbie Houston moved from New Zealand to Baulkham Hills, Australia, in 1978 they didn't realize they were on the brink of starting a global Christian movement. What started in 1983 with 45 people as Hills Christian Life Center has become Hillsong Church, with millions of followers in satellite campuses across the world.

Led by the Houston's eldest son Joel, Hillsong UNITED, the church's modern worship band, has become one of the most successful Christian rock bands in the world. Over the last decade, the group has traveled to 42 countries on six continents, released 11 full-length albums and sold more than 11 million copies. They're the first Christian group to sell out the Los Angeles Staples Center, as well as 10 other major U.S. venues.

Last month, on a cold, rainy night, fans filled the Hammerstein Ballroom in New York to see Hillsong UNITED. We talked to them back stage:

"In 2011, we are pushing the boundaries and stretching ourselves, musically, lyrically and believing that God is going to do things he has never done before," Joel Houston told us, as the group was wrapping up its North American tour.

Part of the group's mission, based on their Christian principles, is to help others. In each tour city, Hillsong UNITED partnered with local churches and agencies to facilitate a food drive. More than 7,000 family meals were collected for those in need. UNITED also raised more than $33,000 for New Zealand's earthquake relief.

"We believe that worship isn't just singing songs; worship is a way of life," says Houston, adding, "It's loving God and others."