Instagram has grown from creating photo memories to creating millionaires. Facebook bought the startup for about $1 billion in cash and stock in a deal that should make co-founders Kevin Systrom and Mike Krieger very happy.

Facebook CEO Mark Zuckerberg said the acquisition will not affect the good things about Instagram, like the ability to share photos on multiple social networks and maintain a personal Instagram circle of friends. “We believe these are different experiences that complement each other,” he wrote in a blog post. “But in order to do this well, we need to be mindful about keeping and building on Instagram’s strengths and features rather than just trying to integrate everything into Facebook.”

Instagram has been downloaded more than 30 million times since its 2010 debut. The company finally released an Android version last week, and it already has been downloaded well in excess of 1 million times.

Systrom said Facebook was not going to fade Instagram into just another Facebook app. “It’s important to be clear that Instagram is not going away,” he wrote in a blog post. “We’ll be working with Facebook to evolve Instagram and build the network. We’ll continue to add new features to the product and find new ways to create a better mobile photos experience.”

This is the first major acquisition for Facebook since solidifying its initial public offering in February. “This is an important milestone for Facebook because it’s the first time we’ve ever acquired a product and company with so many users,” wrote Zuckerberg. “We don’t plan on doing many more of these, if any at all. But providing the best photo sharing experience is one reason why so many people love Facebook and we knew it would be worth bringing these two companies together.”

Related links:

Facebook – Mark Zuckerberg blog post

Instagram – Kevin Systrom blog post

Wall Street Journal – Facebook to Buy Instagram For $1 Billion

GigaOm – Breaking: Facebook buys Instagram for about $1 Billion

NY Times’ Dealbook – Facebook Buys Instagram for $1 Billion

Bloomberg – Facebook Agrees to Buy Instagram Photo App for $1 Billion

USA Today – Facebook to acquire Instagram for $1 billion