All AI ultimately affects people, in some cases deeply buried, in others interacting directly with users, whether physically, such as autonomous vehicles, or virtually, such as recommender systems. In these interactions, AI may be a servant, such as Alexa operating on command; or AI may be the master, such as gig-work platforms telling workers what to do. However, potentially the most productive interactions are a symbiosis, human and AI complementing one another. Designing human-in-the-loop systems changes the requirements of both AI algorithms and user interfaces. This talk will explore some design principles and examples in this exciting area.