From 0 to 200 million users in 3.5 years. Instagram, of course.

From a Foursquare-like check-in app that wasn't really going anywhere to a photo-sharing site holding very nearly 20 billion images via a Facebook buy-out worth $1 billion, Instagram announced today that it's surpassed 200 million users. Or rather, it thanked its users in a blog post for making Instagram great. As a quick reminder, here's how far it has come:

October 2010: Instagram launches December 2010: Instagram clocks one million users (yes, it only took three months) September 2011: 11 months and 10 million users, and it's still iOS only April 2012: 1 million users sign up for the Android version of the app in the space of 24 hours March 2014: Instagram announces it has 200 million users, 50 million of whom signed up within the past six months