Twitter: "What Are You Doing?"

In October 2006 the start-up company Obvious, in San Francisco, launched the social networking and micro-blogging service Twitter: What are you doing?. Twitter "allows its users to send and read other users' updates (otherwise known as tweets), which are text-based posts of up to 140 characters in length." This was under the 160 character limit of the SMS communication protocol for mobile phones.