Two years ago, a team of TikTok employees in China—where the hit video-sharing app’s parent company, ByteDance, is based—were excited to show their colleagues in the U.S. a preview of some new features they’d been working on.

But the Americans were troubled when they saw one of them, which would let TikTok users darken or lighten their skin tone—a feature the U.S. employees feared would spur the creation of culturally insensitive videos featuring blackface, according to three people with direct knowledge of the matter. In another meeting, the China TikTok team showed their American counterparts a different feature that used an algorithm to scan users’ faces and tell them whether they were “beautiful” or not, according to one person who saw the presentation. After some employees raised concerns about the features, TikTok decided against launching them in the U.S.

The episode underscores some of the unique challenges that TikTok, the most consequential new social media platform in years, is likely to face as it elbows aside Facebook, YouTube and other incumbents in the category. In its roughly six years of existence, TikTok has rocketed to more than 1 billion users, recently surpassing Google as the most popular destination on the internet. But just as extraordinary as the speed of its ascendance is the fact that it originated in China, a country that has produced plenty of gargantuan internet success stories—but none of them with the kind of success TikTok has outside China.