The few Vega-type stars whose dusty debris disks have been resolved show this dust to lie in cool Kuiper belt-like rings. However, roughly half of all debris disk candidates exhibit little or no cool dust, since their dust emission peaks at about 25 μm. By analogy with the solar system, these warm disks would lie mid-way between the asteroid and Kuiper belt regions in their systems. Are these disks the Kuiper belt-like rings of a truncated planetary system? Or do they represent the destruction of massive interplanetary asteroid/comet belts? Or maybe these systems are in a transitional stage and have yet to evolve into classically cool debris disks? To answer these questions we need to know where the dust lies, and for that we require the resolving power of mid-IR interferometry with the VLTI.