Interfaces are everywhere and nowhere. They pervade our lives, mediating our interactions with one another, technology, and the world. But their very pervasiveness also makes them invisible. In this seminar, we expose the hidden lives of interfaces, illuminating not just what they are and how they work, but also how they shape our lives, for better and worse. We also discuss a number of pressing social and political issues, such as why we are quick to adopt some interfaces (e.g., smartphones and social media platforms), but reluctant to embrace others (e.g., new voting machines and Google Glass).