If you are a creator on YouTube, you live and die by the algorithm. It's the invisible technology that recommends videos on the trending page or in search results or suggestions all across the platform. No one but YouTube knows exactly how the algorithm decides what to promote and what not to promote. The controversial process has at times promoted fake news and sensational or harmful content. And creators say it's burning them out. Katherine Lo, a visiting researcher in informatics at the University of California, Irvine, studies harassment and mental health in online communities. Molly Wood talks with her about how the YouTube algorithm affects business for creators.