(Update: Harvey Weinstein is certainly not the first powerful man publicly and credibly accused of sexually harassing or abusing women in recent years, but his fall has opened the floodgates in Hollywood. Read more »)

Women are posting messages on social media to show how commonplace sexual assault and harassment are, using the hashtag #MeToo to express that they, too, have been victims of such misconduct.

The messages bearing witness began appearing frequently on Twitter, Facebook and Instagram on Sunday, when the actress Alyssa Milano posted a screenshot outlining the idea and writing “If you’ve been sexually harassed or assaulted write ‘me too’ as a reply to this tweet.”