Biz Stone is flying back to the nest.
In a blog post Tuesday, Stone said he is heading back to Twitter where he'll fill the "Biz shaped hole" he left behind. His top focus, according to the post, is to guide company culture.
Stone will join Jack Dorsey, another of Twitter's co-founders, at the social network, which has a huge cultural presence but has struggled to attract regular users and advertiser dollars. Dorsey has been trying to turn Twitter around since he returned in 2015.
The serial entrepreneur is free to take a new job after selling his most recent company, search engine Jelly, to online scrapbooking site Pinterest in March. Stone says the deal didn't require him to stick around.