Bruce Jenner: 'For all intents and purposes, I'm a woman'

"For all intents and purposes, I am a woman."

With that, Olympian and reality TV star Bruce Jenner put to rest months of speculation about his gender identity. Jenner sat down with Diane Sawyer for an exclusive 2-hour ABC News 20/20 interview to discuss his decades long struggle and how he plans to live his life going forward.

VIDEO: Bruce Jenner, "I am a woman."

Jenner also let his hair down from a ponytail -- a symbolic moment.

"People look at me differently. They see you as this macho male, but my heart and my soul and everything that I do in life -- it is part of me," Jenner, 65, told ABC News. "That female side is part of me. That's who I am."

Jenner says the 20/20 interview will be the last that happens as "Bruce." Going forward, Jenner hopes to emerge as what he refers to as "her."

PHOTOS: Bruce Jenner through the years

"My brain is much more female than it is male," he added. "It's hard for people to understand that, but that's what my soul is."

Jenner revealed that his wives kept his secret for years. He recently revealed the news to his mother and 10 children, who he has told can always call him "dad."

VIDEO: Bruce Jenner was terrified to tell his kids

Jenner says step-daughter Khloe has struggled the most, while Kim has been the most accepting. Ever the fashionista, Jenner says Kim has told him that "he better look good."

VIDEO: Bruce Jenner: Kim Kardashian 'caught me one time' in a Dress

Brandon Jenner says he is "more proud than ever" to be a part of the Jenner family.

Friday, Jenner's children showed their support for the reality TV star ahead of the special.

Brandon posted a photo to Instagram of himself as a child sitting on Jenner's shoulders with the caption "Proud son."

Daughter Kylie also posted a throwback image of Jenner, with Jenner posing in a cropped t-shirt and cut-offs.

She later tweeted that while this has been "very hard," she is proud of her dad, who she called her "hero."

Kim Kardashian told reporters Friday that her family planned to watch Jenner's Friday night interview as they do most things -- together.

"We always support each other. Our family is super supportive of everything that we do and you know we're gonna watch the special tonight and support Bruce and watch it with him tonight," she said.

Following the interview, Khloe Kardashian tweeted that "dads really are heroes."

Kourtney Kardashian tweeted that she was "honored to stand by Bruce's side."

Kendall Jenner said simply, "I love you."

Other celebrities also voiced their support for Jenner.

There are an estimated 700,000 transgender people in the U.S., according to the Williams Institute at the University of California-Los Angeles.

Bruce Jenner and his family will appear on Good Morning America this Monday to talk about what comes next.

ABC News and the Associated Press contributed to this report.

**Editorial Note: During the interview, Jenner referred to himself using male pronouns. ABC News and this station have chosen to follow his lead, though he also referred to himself as "Bruce" and "her."