1. A method of presenting a hierarchically-organized collection of objects, the method comprising: displaying a first-level set of first-level objects in a prominent scale; while displaying the first-level set of first-level objects in the prominent scale, displaying one or more second-level sets of second-level objects in a diminished scale, each second-level set of second-level objects linked to a different first-level object; recognizing selection of a chosen first-level object; and responsive to recognizing selection of the chosen first-level object: zooming a second-level set of second-level objects linked to the chosen first-level object from a diminished scale to a prominent scale; zooming the chosen first-level object from the prominent scale to an enlarged scale; and while displaying the second-level set of second-level objects in the prominent scale and a portion of the chosen first-level object in the enlarged scale, displaying one or more third-level sets of third-level objects in a diminished scale, each third-level set of third-level objects linked to a different one of the second-level objects.