This document provides an overview of styleguides, including why and when they are needed, different types of styleguides, workflows for developing styleguides, techniques and tools, and tips for CSS design. It discusses pattern libraries, prototypes, and repositories as different types of living styleguides. All-in, upfront, and small step workflows are presented, along with their pros and cons. Techniques covered include OOCSS, refactoring, responsive design, and build tools. The document concludes by promoting an upcoming event on frontend automation.