Faceted browsing is a promising way to incrementally refine data sets. Current approaches do not scale well in terms of screen size and have shortcomings in interacting with hierarchical facets. This paper introduces FacetZoom, a novel multi-scale widget combining facet browsing with zoomable user interfaces. Hierarchical facets are displayed as space-filling widgets which allow a fast traversal across all levels while simultaneously maintaining context. We contribute both a seamless continuous navigation and a quick tap-and-center interaction. Two prototypes are described which successfully apply the space-structuring widget to continuous, sampled data and an information collection. A formative user study of the latter indicates that the interface scales well to small screens. FacetZoom is versatile and offers consistent searching and browsing behaviors in a multitude of applications and device settings.