Pattern libraries are a great tool for building sustainable design systems on the web. At their most basic, they are catalogs of reusable components, but they can be so much more. Let's look at some ways to push pattern libraries to the next level, turning them into design tools, API documentation, prototyping interfaces, and beyond. We'll talk about why React is the perfect tool for pattern libraries and design systems, and look at some real world examples to see what's possible.