Building an Android version of its popular, filter-based photo sharing app is a "a major priority" for the team at Instagram, CEO Kevin Systrom told the Guardian recently. Indeed, this is one of the most frequently demanded features for the app, which notoriously only works on iOS.

It may be hard to believe, but Instagram hasn't even been around for a year. It launched for iPhone last October and has since enjoyed enormous popularity, ballooning to 1 million users in just 10 weeks. As of June 2011, Instagram had 5 million users and that number keeps on growing. In early August, the startup announced that its app had published over 150 million photos.

At the same time, another trend has been unfolding: Android is now the most widely used smartphone operating system in the United States and commands over 43% of the smartphone market worldwide.

As Android explodes, why hasn't Instagram released an application for it?

"We're only six people," Systrom told the Guardian. "Android is a major priority for us, but first we have to build the team, and find the best people in the world to work on these projects."

Instagram is indeed hiring engineers, but it's not clear how actively they're looking for seasoned Android developers. The job listings page on their website doesn't explicitly mention Android or Java experience as requirements, but of course, that's not the only channel the company could concievably be using to hire.

Although an Android app is on the horizon, Systrom said that building it was trumped in importance by two projects. First, the camera functionality of the original iPhone app is in the process of being reworked. This will likely include new filters, but from the sound of it, will go deeper than that and overhaul the functionality toward being more of the "social camera" its founders originally envisioned.

The next biggest priority for the Instagram team is building something else that users have been clamoring for: a Web interface. Although numerous third parties have built alternative ways to view Instagram photos outside the original iPhone app, the company itself has yet to offer its own.

Once those two projects are out of the way and Instagram has the right developers in place, Android users may finally get to join their iPhone-toting counterparts in the photo-sharing fun. If its growth on iOS offers any sort of a reliable hint, the company should then expect to see its user base skyrocket even further.