One of Marissa Mayer’s trusted product leaders is leaving for Instagram

Robby Stein, an important product director at Yahoo for most of Marissa Mayer’s time as CEO, is leaving the company for a “product leadership” role at Instagram, he announced Friday, May 13, in an Instagram post.

”As one of the first users on the initial beta, I’ve seen Instagram grow to become the essential visual platform that connects the world, and I am thrilled to reunite with @kevin to help lead this exciting next phase of the product,” Stein posted. “I’m also incredibly thankful to Marissa for giving me the opportunity to build new products and teams at Yahoo the last several years.”

“@kevin,” of course, refers to Instagram co-founder and CEO Kevin Systrom, who met Stein at Google years ago (where Stein also worked with Mayer). Systrom was also an adviser to Stein’s startup, Stamped, which was Mayer’s first acquisition at Yahoo in 2012.

At Yahoo, Stein led the New York engineering office, working on mobile and video products, which had been key to Mayer’s turnaround pitch. Still, Mayer and Yahoo haven’t been able to create meaningful growth, and it now looks like the company will be sold. (Yahoo has also had trouble hanging on to key people brought in through acquisition.)

Not a bad time to head to Instagram, then. The mobile photo-sharing network has been a huge success under Facebook, passing 400 million monthly active users. But it now must prove itself as a business and also increasingly compete for attention with Snapchat.

Systrom recently hired ex-Twitter executive Kevin Weil as head of product, and has now made another major outside product hire in Stein. Another former Yahoo, James Everingham, became Instagram’s head of engineering last year.

This article originally appeared on Recode.net.