First lady Michelle Obama joined the #BringBackOurGirls movement on Twitter Tuesday afternoon.

Our prayers are with the missing Nigerian girls and their families. It's time to #BringBackOurGirls. -mo pic.twitter.com/glDKDotJRt

- The First Lady (@FLOTUS) May 7, 2014

The tweet is signed "-mo," which means the first lady herself penned the message.

The hashtag has become a rallying cry for women and men fighting for the release of nearly 300 girls captured by Boko Haram, a terrorist organization in Nigeria.

In the 23 days since the girls first went missing, the hashtag has been shared over a million times. Many prominent pols-from Hillary Clinton to Michelle Bachman-have joined the movement.

Earlier this week President Obama called the girls' abduction "heartbreaking" and "outrageous."