John Green is Watch Kalakal Onlineexpanding the Vlogbrothers empire.

The Fault in Our Stars author, who recently celebrated the 10-year anniversary of his channel Vlogbrothers with brother Hank Green, has started chronicling his fitness journey in a new vlog called "100 Days."

The channel -- which was designed as kind of a digital version of a New Year's resolution -- follows Green and friend Chris Waters as they document their quest to improve their fitness and health over a 100-day period.

Or as Green describes it in the channel's about page: "Two averagely unfit guys in their (very) late 30s, John and Chris learn from the experts how to make sustainable changes in their lives and have a healthy and productive midlife crisis."

In a recent video, Green talks about the channel and the 10-year milestone of Vlogbrothers.

"Ten years and one day ago I uploaded my first video to YouTube, in honor of that anniversary here's a terrible oldschool Vlogbrothers jumpcut," Green joked before cutting to a clip of their first video.

"I feel so lucky to be at it ten years later. I just want to say thank you to everyone who has been part of the last decade with us."

John and Hank are also selling a series of woodcuts, which are available from their DFTBA store, to celebrate the anniversary.

Throughout 2017, John said he and Hank will continue the Vlogbrothers nostalgia by going back and watching every single one of their videos for a new project called "This date in Vlogbrothers history."