If you spend time on Instagram, chances are you've seen tons of similar photos across your feed in the past day or two with the hashtag #challengeaccepted.
In case you don't know what the heck these black-and-white pictures mean, here's how it works: a woman who's been nominated posts a black-and-white pic of herself, then nominates women in her life, ostensibly as a way to show love and support.
Currently, the hashtag #challengeaccepted has been used on Instagram more than 4.5 million times. It's framed as an international trend of women empowering other women.
The recent impetus behind posting black and white photos of yourself as a "challenge" that is empowering to women is not entirely clear. According to the New York Times, the first woman to post a #challengeaccepted photo was Brazilian journalist Ana Paula Padrão.
There's also been a lot of discussion online about the black and white challenge's potential Turkish origins, but it's not clear if the recent surge of photos is directly inspired by that movement or was sparked by something else.
Despite the confusion, a lot of celebrities have participated:
Taraji P. Henson:
There has also been backlash to the idea that a photo-based viral challenge is substantive or creating concrete change.
As the trend continues to spread, some have opted not to post pictures of themselves, but photos of Breonna Taylor, the 26-year-old woman who was killed by police in her home. People have encouraged nominees to lift the voices of women who need to be heard.
What do you think about the #challengeaccepted trend?
This post has been updated to meet BuzzFeed's editorial standards.