Search engines are now the default way in which most people engage with information, as the vast majority of information is born digital. Also, a new wave of information is underway: low-cost 3D scanners, 3D printers, and powerful modeling software have made 3D models appeal to an increasing audience. Repositories of 3D objects are rapidly growing in both number and size. Yet, the task of exploring such large 3D repositories and retrieving the models of interest remains a challenging problem. Indeed, traditional information access techniques have been shown inadequate to deal with 3D content. Therefore, it is crucial to develop algorithms for content-based searching of 3D object collections; creating compact and accurate descriptors for 3D objects; creating efficient storage structures for databases of 3D objects; investigating theoretical aspects of practical importance, such as the definition of the similarity concept; interfaces for content-based 3D object search; visualization techniques for 3D search results; real time aspects of techniques and algorithms; new challenges such as faceted 3D browsing, social search, and navigation of hybrid datasets. The complex yet concrete problems above are drawing increasing attention from the research community.