When Twitter was born, hashtags were used to get a topic trending. You probably never really paid much attention to the # symbol unless you were going to number something. ie. #1.

Now, the hashtag is everywhere; Instagram more than ever, and it's picking up on Facebook too.

But before the hashtag explosion, what did the # do all its life? Angela Liao of 20px illustrates some of the jobs the # sign kept before Twitter discovered it and made it one of the most-popular symbol on your keyboard: