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ABC News' Jennifer Pereira and Thea Trachtenberg report:

Katy Perry's career is red-hot right now.

In just a few short years, she's sold more than 75 million tracks, earned more than 1 billion YouTube views for her videos and been nominated for eight Grammy Awards.

Now, she's turning her attention - again - to movies. Last year, Perry lent her voice to the Smurfette, the character in the popular animated film "The Smurfs," but her upcoming film release, "Katy Perry: Part of Me," is true to its title.

Part movie and part documentary, "Part of Me" chronicles the singer's extraordinary journey from blonde Christian music singer to multihued-haired reigning queen of pop.

In an interview with Elizabeth Vargas that aired today on "Good Morning America," Perry talked about her motivation for doing the movie, which opens July 5.

Watch the full interview with Katy Perry on ABC News' "Nightline" tonight at 11:35 p.m. ET.

Perry told Vargas that she had just put out her hit album, "Teenage Dream," and people were "really responding" to the songs and the music videos.

"I went to go and book my tour with my management, and everybody wanted to come. And I was like, 'Well, this is interesting. People really are reacting to the record.' I feel like it was, like, a big wave coming. And I thought to myself, 'Well, I think this is going to be a moment. Maybe I should catch it on tape. I'm either going to go completely mental, completely bankrupt, or have the best success of my life," she said.

Perry acknowledged that the film is very personal, but said she didn't hesitate to show that side of herself.

"I think that it was a lesson learned. And that's what's most valuable," she said. "People always ask me, 'What is it that you regret?' And I say, 'nothing, because I could not buy what I've learned.' And I apply those things to my life I learn. And hopefully, hopefully it helps me to be a better human in the future and make better choices."

Behind Perry's colorful exterior is a savvy businesswoman and a genius songwriter.

In fact, when she was asked how she defined herself, she replied: "Well, songwriter first and foremost. When I was 13, I asked for a guitar. And that's how I really started explaining my point of view. And it's kind of like my ammunition. And when I want to get a point across, it's better to write a song when you can sing along … I think at the end of it all, I will always have that to fall back on when I don't fit into my cupcake bra anymore. I will still fit behind my guitar."

Perry is famous not just for her songs, but also for her ever-changing looks, and the movie shows her fans how she's able to transform herself again and again.

"What's with the hair?" Vargas asked.

"The hair? I don't know. I guess it continues to keep growing. And I know that it will. So I'm just trying different things until it stops," she said, laughing. "I just like having fun. And, you know, sometimes I just like to present myself in that fun energy. Because you know, sometimes I'll go head to an event or I'll be at some appearance or whatever. And I don't necessarily get to say, 'Hello, how are you?' to everyone. But when they see me, they know I'm having fun. And when I'm not, I'll stop.'

She has fun, but knows that life isn't perfect. The video for her latest single, "Wide Awake," which was written for the movie, chronicles the last two years of her life, during which her 14-month marriage to comedian Russell Brand ended in divorce.

The movie showcases Perry's heartbreak.

"I thought it would have been strange if I had completely avoided it, because it's, sometimes, you know, when there's a problem, it's not about the problem, it's how you solve it. And you can't avoid an elephant in the room, of course," she said. "But I wanted to be very diligent and respectful about it. And hopefully, you know, people see that problem and they see me having that problem, they're like, 'Oh. Well, even she can't dodge life's curve balls. Even at that level.' And they can relate to me better. That's what I want is, I want that human connection, especially with my fans."

She also spoke about the emotions she displayed in the film.

"I was at different screenings. And I would watch people watch the movie and hear what they would say and listen to them laugh at the funny parts," she said. "And at the very end, I heard, you know, some of the young girls say, 'Oh, we didn't like to see her cry.'

"I definitely did not like to cry, of course," she said. "But sometimes it's good, it's a cleansing."

She told Vargas she was "OK" with having to let her feelings out.

"And I'm OK with showing that real side and stripping that down. I even like the scenes where I left in, in the movie, that maybe weren't under the most flattering lights, and I looked obviously exhausted and tired and bloated and full of zits," she said. "I just wanted to kind of show that, like, really, at the end of it all, I was just a normal girl, pretty plain Jane, who had an idea, planted a seed, and watered it."

Despite the turmoil of her recent break-up with Brand, when Vargas asked her if she still believes in love, she said yes.

"I'm going to let love lead the way, always," she said. "And I was born with this blind - blind ambition, and it's kind of gotten me here to this point. And I think that I'll stick to it. So yes."