Yesterday Laura Bates, the author of Everyday Sexism, retweeted one woman's experience of being masturbated at.
She then began to receive more and more replies describing the same experience.
Within the space of two hours, she'd received over 400 anecdotes.
The replies came from all over the world.
And the incidents happened in all sorts of different public places.
Laura tells BuzzFeed: "This is a perfect example of the kind of sexual offence that many women experience on a regular basis, yet many men would be shocked to hear about."
"It highlights how invisible the problem can be, because there is so little awareness and victims are often made to feel ashamed or afraid, which prevents them from feeling able to speak out."
"The tweets we received highlighted that this happens to victims of all ages, all over the world."
"For many women it has happened on several different occasions."
"Many don't realise it is a criminal offence that can be reported."
The responses continue to flow in to her timeline.
In the Guardian, Laura writes: "Looking at the Everyday Sexism Project database, I realised that in the past two years, 525 women and girls have reported this particular experience. "
"Certain words jump out from the entries, repeated again and again: "frightened"… "horror" … "frozen" … "fear"."
"If you think that being masturbated at is a rare experience, today's torrent of tweets should change your mind."
BuzzFeed has contacted everyone whose tweets have been used in this post for their permission.