Chapter 3 observes the stark contrast between long-standing practices of market opacity and secrecy in the field of cultural property and current legal, professional, reputational, and ethical trends that promote a requirement to engage in due diligence in dealing with cultural property. It then highlights the changing role and scope of provenance research, which has evolved from a highly selective focus on an object’s “career highlights” to promote its value to the task of identifying potential “dark holes” in the chain of title and possession of an item since its creation or discovery. This changing paradigm can be largely attributed to the renewed interest, as of the 1990s, in the history of items that may have been involuntarily lost by their Jewish owners during the Nazi era. This chapter shows how the professionalization and systematization of provenance research, while taking different forms across various jurisdictions in Europe and beyond, may prove essential for promoting provenance research on the history of other cultural items, such as colonial-era objects.