Over eight years ago, Kevin Systrom and Mike Krieger launched a photo-sharing social networking app for iOS devices. Within the first three months, the app had one million users, and the investors came pouring in. A year and a half later, the app had 27 million users, it was finally available for download on Android devices, and the company was offered $1 billion in cash and stock by Facebook. The app has continuously added new features such as hashtags, new filters, video posting, direct messaging, explore feed, photo galleries, stories, and so much more. Today, the app has over 1 billion users, and it is only continuing to grow. This incredible app is Instagram.