On campuses across the country, millions of students have an app called Yik Yak on their phones.
It's like an anonymous version of Twitter. But because it's anonymous, it can get ugly and be a breeding ground for hate speech.
Black student leaders across the country have held sit-ins and protests asking college officials to block the app.
Yik Yak, an Atlanta-based social media app, has a presence on more than 2,000 college campuses. Users of the app post comments anonymously, and anyone in within a radius of a few miles can see, share and rate the comment.