App on which Justin Bieber's account is the most popular

• Photo-sharing social media site
• Popular male to sign 21s here
• "Capture and Share the World's Moments" company
• Popular image manager
• App popular with animals?
• Networking site where popular snappers primarily tag stuff
• 2012 Facebook acquisition
• 2012 billion-dollar Facebook acquisition

Wikipedia Word definitions in Wikipedia
Instagram is an online mobile photo-sharing , video-sharing , and social networking service that enables its users to take pictures and videos, and share them either publicly or privately on the app, as well as through a variety of other social networking ...