Archives are the factories and laboratories of the historian. Along with private studies and public libraries, they are the loci of our apprenticeship as scholars and the warehouses from which we acquire the materials to build the history we write. Until recently, however, scholars of the early modern period (as of other eras) rarely paused to consider how and why these repositories came into being, despite the fact that these processes have fundamentally shaped and coloured our knowledge of the past. Too often we mine the documentary sources they house without scrutinising the decisions about selection, arrangement, preservation, and retention taken by those responsible for the care of their contents over successive generations. We still fall into the trap of approaching them as if they provide a transparent window through which we can view societies remote from us in time.