If you use technology to follow conversations and trends on social media -- on Twitter, Facebook, Instagram, Tumblr—you know to look for the hashtag. In our current digital age, the hashtag identifies movements, events, happenings, brands—topics of all kinds. The hashtag sign didn’t always have this meaning, though. It’s had a few different lives. The KALW podcast 99% Invisible tracked the history of this sign in their episode “Octothorpe”.