Explore the inner workings of CSS preprocessors in this 26-minute conference talk from CSSconf.eu 2013. Dive deep into the parsing and compilation process, understanding how preprocessors transform your code into valid CSS. Learn about the structure of parsed data, including rules, group structures, and variables. Discover how syntax trees are created and manipulated. Examine the compilation process and see how the final CSS is generated. Gain insights into introducing custom modifications for unique results. Perfect for developers looking to demystify the "black box" of CSS preprocessing and enhance their understanding of front-end development tools.