Nucleus is free CMS software which helps you to build your blog. Nucleus supports multiple blogs under one account, multiple authors, categories and much more. It has a built-in commenting system. Nucleus can provide URLs optimized for both readers and search engines if your web server supports. Your Nucleus site looks is fully tweakable through skins and templates, and multiple CSS files. Next to that, the language used by the Nucleus admin area can easily be changed through language-files. Additional features can be programmed in so called plug-ins.