Beyoncé is Sasha Fierce

When she's not playing Sasha Fierce, you can catch Beyoncé on the big screen. After her showstopping performance in Dreamgirls, Beyoncé took on another big role—Etta James in the upcoming film Cadillac Records.

At first, Beyoncé says she wasn't sure she could handle the role. Etta James not only had a big voice—she also struggled with addiction. "I was afraid because I have one scene in the movie where I almost overdose on heroin and every other word out of my mouth is profanity," she says. "I was afraid that I wasn't ready for a part so dramatic. And my mother said, 'What's wrong with you? You're absolutely ready.'"

With her family's support, the help of an acting coach and a lot of research, Beyoncé dove into the role headfirst. "I studied Etta James, but I did not want to mimic her. I wanted to do my own interpretation," she says. "I visited the Phoenix House [a drug and alcohol treatment facility]. I met a lot of people, and they answered a lot of questions because I wanted to understand the need for the addiction."

Beyoncé says Etta James is the most fulfilling role she's ever played and she loved working with Cadillac Records director Darnell Martin. "I completely trusted her and she trusted me, and [co-star] Adrien Brody was incredible," she says. "I'm only in the end of the movie, but it's an ensemble cast and it's a story that needs to be told."