In April, Facebook announced a cash and stock deal to buy Instagram that was said at the time to be worth $1 billion.
Following the slide in Facebook's share price since it listed in mid-May, the deal is now thought to be worth around $730m, but that is still a dizzyingly high figure for such a young company.
The acquisition was delayed while it passed unscathed through regulatory scrutiny in the US and Europe, and the companies have now officially announced completion of the deal.
In a blog post, the Instagram team celebrated the development and confirmed that more than 5bn photos have been shared on the iOS and Android apps by around 80m Instagram members.
"We're humbled that so many people around the world use Instagram to share their lives with friends through photos," the firm said.
"From weddings to epic pilgrimages through the Spanish countryside, we're constantly amazed by the stories that are shared on Instagram, and we thank you for being a part of this growing community.
"What makes this even more exciting is that our deal with Facebook has closed, which means we can now work together to evolve and build a better Instagram for everyone."
"The Instagram app and its features will stay the same one you know and love, and we'll keep working together to build a better Instagram for everyone," they said.
Facebook's Mike Schroepfer also said in a separate blog post that the social network was "committed to building and growing Instagram independently".
"So many of us at Facebook love using Instagram to share moments with our friends. And for so many people, sharing photos with friends is an important part of the Facebook experience. That's why we're so excited to bring Instagram to Facebook and see what we can create together," he said.
"As we said from the beginning, we are committed to building and growing Instagram independently."
"We also can't wait to work with the talented Instagram team to improve the mobile experience."
It is Instagram's ability to create a winning mobile experience that Facebook values the most, as there have been concerns that the listed social network has been slow off the mark with smartphones and tablets.
An ever growing number of users now access Facebook on mobile devices, but some analysts feel the company is behind the game in terms of innovation, causing its share price to fall by around 50%.
In acquiring Instagram, Facebook gets access to a hugely popular photo-sharing app that is used by millions of people, but also many of the world's top brands in marketing campaigns. It is now just a matter of working out how to make money from that.