On the evening of August 23, 2011, Chris, a New Yorker who wishes his surname to be withheld, created a Tumblr account. His aim was to raise awareness of the Occupy Wall Street march planned for September 17. The idea was simple: he asked users to submit a photograph of themselves holding a sign explaining their economic circumstances. He called the page We Are The 99 Per Cent, and promptly forgot about it.

Four days later, Chris returned to his flat, after spending time preparing meals for protesters, and checked the We Are The 99 Per Cent tumblelog. When he had left, there had been two photos in the inbox. "I thought, I'll have five or six more submissions," says Chris, now 29. "The inbox was overflowing. I spent that night reading through the submissions. By the time I was done, I had barely dented this thing."

One photo was from Priscilla Grim, a 36-year-old activist working on strategic communications for the Occupy Wall Street movement who has been "protesting one way or another for about 20 years". Grim noticed that, two weeks after submitting her image, the blog hadn't been updated, so she emailed Chris and offered to help to edit the blog: "It struck me that this was the perfect organising tool of today," she says. Together, they started posting the submissions. Some were short: "I served in the US Army. Served 16 months in Iraq. Now I deliver pizza. I am the 99%." Others were longer, from the jobless woman prevented from donating a kidney to her friend because she didn't have health insurance, to the 19-year-old single mother who said she went without food for days to buy formula milk for her four-month-old son. But they all kept the same format, with signs often obscuring the creators' faces. "We posted 100 photos before it went big," says Grim. The New York Times covered the blog. "After that, it went all over the place."

The blog became a meme and the meme went viral. As Wired went to press, 3,000 photos had been posted; the tumblelog receives ...