The message was cryptic. Two words. No context, no punctuation, just: "inviting coworkers"

But that short statement proved to be enough to launch a global phenomenon that has launched careers, reunited long-lost relatives, and even, some would argue, topple dictators.

It was the first tweet.

Since Twitter co-founder Jack Dorsey posted it on March 21, 2006, Twitter has registered nearly 200 million users who now post more than a billion tweets every week.