Instagram co-founder and CEO Kevin Systrom has said it's their job to keep the internet "as safe as possible".
He spoke to Newsbeat ahead of the app's fifth anniversary.
When asked about the biggest challenge since launching in October 2010, Kevin joked, "Which one?"
He's been asked about nudity rules before. But with users still being able to stumble across inappropriate content on the app, Kevin said it's still one of their biggest concerns.
"At the scale of 400 million [users], you're bound to get some stuff that isn't quite right," he said.
"But, you know, it's the internet and it's our job to try to keep it as safe as possible and we have entire teams back at the home base making sure that that's true."
When Kevin started Instagram with Mike Krieger (left) it was made up of 13 staff
Instagram's terms of use say: "You may not post violent, nude, partially nude… pornographic or sexually suggestive photos."
Expanding on the app's rules around inappropriate material, Kevin explained: "We don't allow it but we rely on community members basically who find content that is objectionable or against our terms to flag it and then we remove it.
"But if you post it we'll make sure to take it down."
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Instagram claims to be "the fastest growing social media platform on the planet", with an estimated 80 million photos uploaded every day.
"Five years - it went by really quickly but it feels like a lifetime," said Kevin.
"We had no idea when it launched it would get to this point. It's been a long road and an exciting one."
So what's next?
Kevin explained that originally a glitch stopped hyperlinks being put in captions, but there are still no plans to introduce them
He explained having an exclusive clip of Star Wars VII: The Force Awakens was "pretty awesome".
But as for the future he's tight-lipped about upcoming features, even though he admits "food, photography, sports etc" could all "take off on Instagram".
He said: "I think it's about having a vision for where you want to go.
"And where we want to go is making sure that you can see the world happening around you in real time.
"The launch of trending places and trending tags in the US is the beginning, it's a hint of what's to come globally and I think you'll see that developing over the next year.
"I think the biggest challenge over time is that we stay creative and making sure that we continue to launch awesome products that people love," Kevin said.
"The good news is we've been very fortunate to do that over the last five years."
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