Hi Freya... Only with Poser 5! Poser 4 cannot have sub-folders in the library folders. Even with Poser 5, it's a pain to navigate through lots of sub-folders in the library panel. PBooost works differently to sub-folders by allowing you to make 'lower-level' banks of content. Each library type (characters, pose, etc.) can be divided into a series of 'banks' like 'Vic3', 'Vic1', 'Mike', 'Default', 'Steph' etc. Each bank can have a whole array of folders and sub-folders within it. There's then room for you to have your poses AND mat files in the appropriate pose banks and still be able to find what you want! With PBooost, you then switch each library to the bank you want and only that content then appears in the library tab in Poser. Hope this makes sense! Howard:))