Twitter co-founder Biz Stone is working on another startup.

According to Kara Swisher at All Things D, Stone’s new project is called “Jelly,” which her source called a “native mobile” effort.

That’s pretty vague, and the only other tidbit provided was that the product will likely “be aimed and smartphones and tablets.”

Apparently, Stone has already hired four or five employees to work on Jelly.

In 2011, after leaving his day-to-day role at Twitter, Stone put his attention into Obvious, which says that they “do various things.”

Obvious, which Stone launched alongside other Twitterites Evan Williams and Jason Goldman, is involved in blog platform Medium, as well as Lift, Branch, and a handful of other products.

Biz Stone was recently granted inventor status when his name, along with Jack Dorsey’s, appeared on an approved patent for Twitter. Yes, the entire concept of Twitter wasn’t patented until earlier this month.