Through a post on its official blog, image-sharing service Instagram announced that it has reached the milestone of hitting 400 million users just nine months after it achieved 300 million users.

Instagram's growth seems to be reliably steady upon the achievement of the new mark, and in the blog post, the company said that Instagram's community continues to evolve into being more global, with over 75 percent of its users located outside the United States.

For the last 100 million users who joined the service, Instagram noted that over half are located in Asia and Europe, with most people signing up from Brazil, Indonesia and Japan.

The blog post also highlighted several celebrities who are among the 100 million newest members of Instagram, namely soccer superstar David Beckham, Caitlyn Jenner, Raffi and Nagita from Indonesia, Real Madrid midfielder Toni Kroos and T.O.P. of South Korea.

Also highlighted in the blog post are several pictures uploaded to the service, such as the first image of the surface of Pluto, celebration for the Champions League, white pools of Turkey and a ghost town in the Namibian desert. These photos, however, are just a handful of the 80 million pictures that are uploaded daily on Instagram.

"When Instagram launched nearly five years ago, 400 million seemed like a distant dream. Now, we continue to strive to improve Instagram—helping you experience the world through images and connect with others through shared passions," the blog post concluded.

Instagram's growth, while impressive, will need to continue if it wants to catch up to the user base of Facebook. Back in 2012, the leading social networking site acquired the picture-sharing service for $1 billion in cash and stock. Instagram's 400 million users is still less than half of the over 1 billion monthly active users reported by Facebook, and is also less than other Facebook-owned apps WhatsApp, with 900 million users, and Messenger, with 700 million users.

There were some concerns that Instagram's advertising service would turn away users from the app, but that does not seem the case with the service's continued expansion.

Research company eMarketer expects the global mobile advertising revenue for Instagram to come in at $595 million this year, with the figure escalating to $1.48 billion next year then $2.81 billion in 2017.