CHRIS MESSINA invented the hashtag in 2007. This single keystroke—originally called the number sign or pound sign—has become the defining communication symbol of our age (#BlackLivesMatter, #MeToo). For a symbol that has galvanized social movements, influenced presidential elections, elevated brands and destroyed reputations, the hashtag’s origin story is pretty nerdy. The hashtag was created after the 2007 South by Southwest Interactive conference in Austin, during which tweets on the one-year-old Twitter service went from 20,000 per day to 60,000 as conference attendees chatted incessantly among themselves and dominated Twitter. (Today, 500 million tweets cross Twitter every day.) Messina attended the conference, and recalls that “there were a lot of people back in San Francisco frustrated that their Twitter feeds were full of stories from Austin that were not relevant to them. There was no way of organizing tweets so you knew what to pay attention to.” Four months later, in August 2007, Messina was at a smaller conference called BarCamp at which the danger was not that the conferees would overwhelm Twitter but that they would overlook one another’s tweets. To make their tweets easy to locate, Messina urged BarCampers to tag their tweets #barcamp. The hashtag was born from this sensible suggestion and quickly caught on.

According to Chris’s website, he “spent a decade living on the edge of social technology. He has designed products and experiences for Google and Uber, founded startups, and changed the world by giving away many of his creations, including the hashtag.”