A few months ago, Twitter co-founder and former CEO Evan Williams announced that he was leaving Twitter. This came just after it was revealed that co-founder Jack Dorsey was returning to lead product, and six months after Williams handed the CEO reins to Dick Costolo.

Now, Biz Stone, the other co-founder, has announced that he too is stepping back (not completely away) from Twitter.

Stone and Williams are trying their hands at a new (or resurrected rather) startup called Obvious, along with former Twitter VP of Product, Jason Goldman. Here’s what it says on the Obvious site:

The Obvious Corporation makes systems that help people work together to improve the world. The proliferation of technology can seem superfluous, but with the right approach, technology can benefit individuals, organizations, and society. We are relaunching the company that originally incubated Twitter with a high level of commitment to making a difference and developing products that matter.

In more than a decade of developing large scale systems on the Internet, we’ve never been more excited than right now. The possibility to reach and connect expansive numbers of people fundamentally changes the nature of what’s possible when it comes to building businesses on the Internet. Also, there’s room for innovation in how businesses measure success and more meaningful definitions of ambition.

Stone, Williams, and Goldman all used to work on Google’s Blogger team. Then, Williams left, and the other followed him into Obvious, and eventually Twitter was born. Now, it seems that they’re going back to where they can make new things, rather than work on their creation that proved to be a succes, which is now largely in the hands of its other co-founder Jack Dorsey and CEO Dick Costolo (also formerly of Google).

On his personal blog, Stone writes:

My work on Twitter has spanned more than half a decade and I will continue to work with the company for many years to come. During this time—especially lately, it has come to my attention that the Twitter crew and its leadership team have grown incredibly productive. 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.

As for the bulk of my time day-to-day, I’m thrilled to announce that Evan Williams, Jason Goldman and myself will be relaunching The Obvious Corporation as co-founders. Our plan is to develop new projects and work on solving big problems aligned along a simple mission statement: The Obvious Corporation develops systems that help people work together to improve the world. This is a dream come true!

When Williams stepped down from Twitter, he also noted that he would remain on the Board of Directors, so it appears both he and Stone will still remain close to Twitter, just not as hands on as they once were.