Instagram is officially bigger than Twitter, and it has the power to let marketers target audiences at the same level as its parent company Facebook. If you’re not taking it seriously as a marketing channel yet, what are you waiting for?

How have you leveraged Instagram in your marketing efforts? If you haven’t, what is holding you back? Discuss.

Last week, Mark Zuckerberg and Instagram announced that the image and video sharing service has surpassed the 400 million monthly active users mark. It has added 100 million just since December.

As Instagram rapidly grows its user base, it is also becoming a more accessible marketing platform to businesses of all sizes. Earlier this month, the company announced it is opening up its ads to all starting this month with launches around the world on September 30. The ads utilize Facebook’s ad infrastructure and targeting so marketers can target users based on well-established interests.

“Businesses of all sizes have been testing these new capabilities this summer with positive results, and we’re seeing significant demand, particularly in areas like e-commerce, travel, entertainment and retail,” Instagram said in a recent blog post. “We’re thrilled to see what brands can achieve in the months ahead using Instagram as their creative canvas.”

With Instagram going so far as to surpass Twitter in active users, one has to imagine that businesses will only just be getting started when it comes to both paid and organic promotion.

“While Instagram may be a relative newcomer on the social media scene, there’s a strong business case for it becoming a part of your marketing strategy,” says Jayson DeMers at Forbes. “For instance: Did you know that at last count, nearly 28% of the US population uses Instagram, and that nearly half of all US adult users use it daily? Instagram is also beneficial from a revenue perspective, with the average order value from referrals being $65; this is second only to Polyvore’s $66.75.”

It’s worth noting that while so many in the U.S. use Instagram, 75% of its user base lives outside the country. Among the last 100 million join, Instagram says, over half live in Europe and Asia. Brazil, Japan, and Indonesia are the countries that added the most.

“Instagrammers continue to capture incredible photos and videos from all corners of the earth (and even the solar system),” the company said. “We’ve seen the first surface image of Pluto and the Champions League celebrations, as well as striking locales like the white pools of Turkey and a Namibian desert ghost town. These are just a few of the more than 80 million photos per day shared on Instagram.”

As it’s still early days, marketers have a lot to figure out with Instagram and a lot of testing to do. Sure, some have attempted to crack the science, but with ads only just becoming available to all, not to mention increased competition among marketers, things are only going to continue to evolve, just as they have with Facebook.

David Kirkpatrick at MarketingDive writes, “Devising when is the best time to post on social media is notoriously tricky. Mavrck analyzed 1.3 million Instagram posts and found more posts went up in the afternoon and evening, and suggested marketers looking for engagement might want to take advantage of the morning hours before noon. During this time users still monitored their feeds but weren’t actively posting themselves.”

Instagram has so far been limited when it comes to B2B use, but a few months ago we looked at a report from Social Media Examiner indicating that 40% of B2B marketers intend to increase their Instagram activity.

Do you see Instagram as an important part of your online marketing? Share your thoughts in the comments.