Debris disks are disks of dust that surround a significant fraction of stars of a wide range of masses and ages. From dust lifetime arguments it is inferred that these particles originate from the collision of planetesimals, similar to the asteroids, comets and KBOs in our Solar system. Our Solar system also harbors a debris disk and some of its properties resemble those of extra-solar debris disks. The study of the debris dust helps characterize the extra-solar planetesimal belts (location, composition...), a population that would otherwise remain undetected in the foreseeable future. This talk will discuss the lessons learned from the extensive debris disks surveys carried out by Spitzer, the on-going debris disks studies with Subaru and Herschel and the prospects for the future.