Co-founder Biz Stone is leaving Twitter to join Evan Williams and Jason Goldman to reboot the web media incubator, Obvious Corp. from which Twitter originated.

Just a few months after co-founder Jack Dorsey returned and former CEO Evan Williams left the real-time short messaging service, Biz Stone announced of his move.

bizstone.com:

bizstone.com: Biz Stone leaves Twitter

Stone said, he will still continue to be with Twitter in and as needed advisory role. William remains on the company's board despite having stepped aside from an operating role in March.

San Fransisco based Twitter issued a statement saying, We're excited for Ev, Jason and Biz and look forward to seeing what they create as they return to their entrepreneurial roots with Obvious. Twitter is lucky to have all three of our founders still deeply connected to the company.

Stone posted a blog praising the work of Twitter's leadership and said, I've decided that the most effective use of my time is to get out of the way until I'm called upon to be of some specific use. He added that Costolo has been very supportive in thinking this through with me so I can focus on new endeavors while remaining a strategic asset to Twitter.

He also said, apart from working on Obvious and occasionally with Twitter, Stone plans to spend more time helping Schools and non-profit organizations.