We spend our lives working with systems created by other people. From the UI on our phones to the cloud infrastructure that runs so much of the modern internet, these interactions are fundamental to our experience of technology - as engineers, as developers, as users - and user experiences are viral. Great user experiences lead to happy, productive people; bad experiences lead to frustration, inefficiency and misery. Whether we realise it or not, when we create software, we are creating user experiences. People are going to interact with our code. Maybe those people are end users; maybe they're the other developers on your team. Maybe they're the mobile app team who are working with your API, or the engineers who are on call the night something goes wrong. These may be radically different use cases, but there's one powerful principle that works across all these scenarios and more - and it's called discoverability. In this talk, we'll draw on ideas and insight from user experience, API design, psychology and education to show how you can incorporate discoverability into every layer of your application. We'll look at some real-world systems, and we'll discuss how how discoverability works with different interaction paradigms. Because, whether you're building databases, class libraries, hypermedia APIs or mobile apps, sooner or later somebody else is going to work with your code - and when they do, wouldn't it be great if they went away afterwards with a smile on their face?