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Preprocessors for CSS are a controller/scripting way to think about your CSS using SASS/SCSS. The preprocessor will read your SASS code and write (or compile) your code to common CSS. This is great as it lets you organize your CSS while still keeping the http call to one connection when loading your styles. Preprocessor is much like the Back End of a server but this one is for our CSS. It lets us to organize our code importing snippets of written CSS with a SASS file.