Very few techniques have been presented in the literature for shape representation that have combined both region and boundary information at multiple scales. We introduce such a novel technique in this paper. Our algorithm is an implementation of a two-dimensional dynamic grassfire that relies on a distance surface on which elastic contours minimize an energy functional. A Euclidean distance transform combined with the active contour model, referred to as a "snake", is used for this minimization process. Boundary information is integrated into the model by the extraction of curvature extrema and arcs of constant curvature. We do so by introducing a new technique based on operations derived from the field of mathematical morphology. The principal advantages of our new method compared with previous algorithms for shape description based on skeletonization are: implicit connectivity of the skeleton, smooth and accurate results, integration of region and boundary information, multiscale description and hierarchical representation in terms of feature significance. Furthermore, new possibilities are offered within the context of our method. For the first time, dynamic (deformable) skeletons are naturally defined. Also, our method easily permits user interaction which can be used for the generation and comparison of different types of skeletons. Finally, the graph representation of the skeleton is straightforward to obtain, a fundamental step for shape analysis. Our new method for shape skeletonization is the first to address these issues which are fundamental to the description of natural forms.