Thousands of teenagers were screaming, wailing for a beautiful, young woman a global pop star far from home who was spending a very special night backstage practicing her Japanese. The beautiful, young woman is Beyonce Knowles, on tour in Tokyo. On this night in September, she turned 25. That she chose to celebrate this day far from friends, family and home is just part of being Beyonce, we learned. “I’m just now starting to get it balance,” Knowles said. “I’m starting to learn to take care of myself, and usually, it’s all or nothing. I work really, really hard, long hours, or I do absolutely nothing.” Watch the full story on “Nightline” at 11:35 ET tonight.

And over the last few months of watching her behind the scenes, from Tokyo to Chicago, we never saw Knowles doing nothing. We saw a major contender for the hardest-working woman in entertainment who endured grueling 15-hour days, a work ethic based on unrelenting pace. “I was really exhausted when I was in Japan,” she said. But exhaustion is no excuse for Knowles. “I know when people are in the audience they come to see they want to see a show. They want to live out their fantasies,” Knowles said. “And I see when I am looking in the audience it doesn’t matter how sad or how weak or whatever emotion they feel. For that two hours they think they are me. So they don’t want to see something boring, so I give them a show.”