If you've been on Instagram lately you've probably noticed the slew of black and white photos that have seemingly taken over the app. Based on the caption of these posts it is some sort of challenge, which begets the question: What is "Challenge Accepted?"

The answer is simple. The latest challenge to take over the social media app is one that aims to highlight women and encourage them to support other women as well. Celebrities from award-winning director Ava DuVernay, to actors Kristen Bell and Kerry Washington, and reality star Khloe Kardashian, just to name a few, have all participated in the challenge thus far.

While most of the women who have participated were nominated by someone else, there is nothing against someone starting the challenge on their own. In either case, nominated or not, the trend seems to be that the poster then nominates women in their life to participate as well.

At publishing time, there are over 4.3M posts containing the #ChallengeAccepted hashtag on Instagram and it's only growing. On Monday, a spokesperson for Instagram told The New York Times, "The trend is still picking up with usage of the hashtag on Instagram doubling in the last day alone."

"Based on the posts, we’re seeing that most of the participants are posting with notes relating to strength and support for their communities," they added.

Another hashtag that has been accompanying these posts is #Womensupportingwomen, which has over 7.1M posts.

The Instagram logo is pictured. AFP/LOIC VENANCE