Facet Folders are a visualization and interaction concept for filtering collections of personal data. Although visually derived from the ubiquitous folder hierarchies of file managers, Facet Folders explicitly expose the faceted metadata used for filtering. Facet Folders can be arranged into persistent hierarchies, enabling the construction of dynamically updating views across multiple facets. If demands change, the hierarchy can be easily rearranged. Keywords Faceted browsing, filtering, folder hierarchy, PIM ACM Classification Keywords H5.2 Information interfaces and presentation: User Interfaces - Graphical user interfaces (GUI).