Twitter’s 7th birthday: See celebrities’ first tweets and a video timeline

Twitter celebrates its 7th birthday day — marking the first public tweet sent on March, 21, 2006: More than 1 billion tweets have been sent since.

First tweet ever sentTake a look back at celebrities’ first tweets (see more at USA Today):

Neil Patrick Harris first tweetEllen first tweetJames Cameron first tweetAnd finally see Twitter’s video showing its timeline — tracking the first hash tag and first retweet (in 2007) to the first tweet from space: