Just one year after leaving Facebook over differences with CEO Mark Zuckerberg regarding the tech giant's direction, Chris Cox is returning as its chief product officer.

“Facebook and our products have never been more relevant to our future,” Cox said in a post announcing his return. “It’s also the place I know best, and the best place for me to roll up my sleeves and dig in to help.”

Cox left the company when it was moving toward a unified, encrypted messaging system within its family of apps -- Facebook Messenger, Instagram and WhatsApp.

"It's a product vision attuned to the subject matter of today: a modern communications platform that balances expression, safety, security, and privacy. This will be a big project and we will need leaders who are excited to see the new direction through," Cox said at that time.

Cox has spent some of his time away with his family, on climate change initiatives and on building a progressive political infrastructure, according to his post.

"In the past month the world has grown more chaotic and unstable, which has only given me more resolve to help out. Our most important decisions and products are ahead of us," he wrote.

In a brief post, Zuckerberg welcomed him back into the fold by saying he's "really excited" that Cox has returned.