React has caught a lot of criticism for the full mixing of HTML and JS, but it is a large portion of the rising tide of the JS landscape today - and many more websites are componentizing all the parts of the front end. Why are we leaving our CSS behind in giant stylesheets? CSS deserves the improved scope and modular building that we incorporate into today's HTML and JS. The goal of this talk is to approach the pros and cons of several different styles of handling CSS in a modular way, and reveal myths about performance that hold many back. While focused on React examples, the core takeaways about modular CSS are not dependent on React, and apply to most component-based UI.