(NEW YORK) -- Seven years ago on Thursday, the first tweet ever was sent.

That tweet, sent by Twitter co-founder Jack Dorsey on March 21, 2006, read, "just setting up my twttr."

Since then, the social network has grown exponentially, pumping out millions of tweets a day.

"There are currently over 200 million active users, and they send over 400 million tweets per day.  So, that means, just over every two days there are a billion tweets sent," says Twitter spokesperson Elaine Filadelfo.

As for what the all-time top tweet has been to date, Filadelfo says, "The most re-tweeted tweet of all time was from President Obama on election night when he tweeted 'Four more years.' That has over 800,000 re-tweets."

Copyright 2013 ABC News Radio