kevin systromReuters Pictures/Lucas Jackson

After eight years, the founders of Instagram are leaving the company. 

CEO Kevin Systrom and CTO Mike Krieger announced Monday that they are departing the mega-popular photo sharing social network , which was bought by Facebook for $1 billion in 2012. The news came following months of turmoil and scandals for Facebook, and reportedly comes amid tension between the founders and Facebook CEO Mark Zuckerberg. 

Still, it’s something of a surprise that Systrom and Krieger would leave the app they built from scratch. Instagram grew out of Systrom’s love of photography, and has since become one of the most popular social media apps in the world — in fact, Instagram hit 1 billion active users earlier this year. 

Here’s how Systrom got his start and built Instagram into what it is today.