This tool allows you to select a block of HTML, then customize CSS selectors for each of the child elements. The resulting block of CSS is considered “modular”, in that the corresponding HTML must follow a particular structure. Yes, this is already the basic concept behind CSS selectors, but stylesheet selectors tend to be much more vague and unorganized. This allows you to control and recognize the scope of styles much more easily.

This tool also makes use of jQuery.paneSizer.