Lizzie Velasquez, the subject of upcoming documentary "A Brave Heart," didn't realize she was different until the first day of Kindergarten, when classmates shunned her at school. The 26-year-old was born with neonatal progeroid syndrome, a genetic condition that impacts her appearance and prevents weight gain, and this made her an easy target as a young child.

"The other kids were scared of me, pointing at me, not wanting to sit with me," she told TODAY in a new interview. "I couldn't process it. I wasn't doing anything to them, so why was it happening to me? And I didn't dare tell anyone."

"Ugliest Woman in the World"

Perhaps her lowest moment, however, was browsing YouTube at age 17 and stumbling upon a video of herself alongside the words "Ugliest Woman in the World." The clip, which had more than four million views, prompted a slew of horrible comments from fellow YouTube users, some of whom said Velasquez should be killed and questioned why her parents didn't abort her. The cruelty overwhelmed Velasquez, who was already at a vulnerable age.

"I read every single comment thinking there would be one person to stand up for me," she told TODAY. "Not one person said, 'She's a child, leave her alone,' or 'You don't know her story, why she looks like that.' I felt like someone was putting a fist through the computer screen and physically punching me. I bawled my eyes out."

As hurt as she was by all the online bullying, Velasquez rose above the negativity. She enrolled in college and now feels thankful for the person who dubbed her the "ugliest woman in the world."

"I realized I could use [the teasing] for the greater good," she told TODAY. "I went to college, became a motivational speaker and wrote a book."

Lizzie Velasquez's moving TED Talk

In 2014, Velasquez did a TED Talk about how to define oneself no matter what others say.

"Am I going to let the people who said [about me] 'kill it with fire' define me? No," she said to ample applause at the TED Talk.

The video went viral online and famous figures gave Velasquez ample praise for standing up to her bullies.

"When I heard her [TED Talk, [it] knocked me out and showed me how she triumphed over the truly ugly people," Whoopi Goldberg said on "The View" last year. "It made me stand up and cheer."

How the TED Talk landed her a documentary

Following the TED Talk's positive reception, TEDWomen event producer Sara Hirsh Bordo asked Velasquez if she could do a documentary about her life, and that's how "A Brave Heart" was born.

"A Brave Heart," however, isn't solely Velasquez's story. She made it clear at the beginning that she wanted to address the larger issue of bullying in the documentary and not simply focus on her own personal struggles.

"I told [Bordo] I didn't want the documentary to be just another longer version of my TED Talk and I don't want it to be just about me," Velasquez told TODAY. "That was important to me. When you see the film, it is my story, but it's also everyone's story. People can relate to being bullied or feeling insecure or being embarrassed by their looks."

Velasquez's brutal but honest thoughts about bullying

Though she is doing her best to highlight the problem with bullying, Velasquez believes it will always be a problem in society and that it's up to her and others to try and prevent it as much as possible.

"[B]ullying will never end—ever," she told TODAY. "It's a big reminder that there is work to do to ensure others do not feel alone. We have to show them there is light at the end of the tunnel."

If you are a victim of cyber bullying, call the Cyber Bullying Hotline at 1-800-420-1479 to report bullying and receive help.