This Is Sheryl Sandberg's Favorite Facebook Page: 'My Stealthy Freedom'

It's called "My Stealthy Freedom" and it shows Iranian women risking severe punishment by daring to take off their head scarfs out of doors.

Sandberg, with her Lean In organization (and best-selling book of the same name), is one of the nation's best-known feminists these days. She mentioned her favorite site on stage at the Fortune Most Powerful Women conference on Tuesday, when talking about her favorite part of her job.

"What drives me, and I'm sure it's true for so many of the amazing women in this room. You want to make a difference. That means making someone else's life better. What I love about Facebook is that we give people a voice," she said.

She named My Stealthy Freedom, which shows selfies of bare-headed Iranian women, and their stories, as an example. Sandberg got a bit choked up when she talked about her favorite picture on the site, which she had someone translate for her. "The grandmother writes, 'I wanted granddaughter to feel wind on her hair before it goes gray.'"

The page has nearly 670,000 likes and is such a phenom that Iranian-French artist Aiden Nakhlband has started painting women from the photos on the site.