Controversy over the first tweet does exist. Many report this as the first tweet by Dorsey but note that this time stamp is 12 minutes later than previous one.

Twitter co-founders Evan Williams (left) and Biz Stone.

The character limit of 140 was established because that's the maximum number of characters allowed on a phone text message - minus the address.

Here is co-founder Jack Dorsey (left) hanging out with Qik’s Daniel Brusilovsky at iPhone Dev Camp 2 in 2008.

Twitter had 8 employees in 2006. There are now over 400.

Twitter's first logo. Twitter was created by Dorsey, Stone and Williams at the podcasting company Odeo. The three plus other Odeo members formed Obvious Corporation to break off Twitter from Odeo in October 2006.

Twitter's current logo for light pages.

The most popular tweeter is Lady Gaga currently at 21,235,225 followers.

One of the first "funny tweets" posted by Twitter in 2006.

Twitter's first baby.

First announced firing on Twiiter (2006).

First announcement of a Web site launch on Twitter in 2006.

One of the first reviews of Twitter from Airbag Industries in 2006.

One of the first Twitter apps in 2006, the "twadget."

Another 2006 Twitter app.

Here's "Twapp" from 2006.

A screenshot from Twitter in 2006.

Twitter first gained notoriety as a dumb app that let people Tweet anything irrelevant but it has lately been a critical tool for breaking news - from political unrest throughout the world, the spread of information during natural disasters such as the Japanese earthquake, and waiting in line for the new iPad.

Twitter rescheduled maintenance time in 2009 to keep lines of communication open during  a crisis in Iran.

Martha Stewart gives critical pie-making tips.