The production of big pictures is arguably the most significant sign of the intellectual maturity of a field. It suggests both that the field's broad contours, refined over several generations of scholarship, enjoy the approval of practitioners, and that audiences exist with an interest in or need for overviews. The situation is somewhat more complicated in the history of science, since the existence of big historical pictures precedes that of a well-defined scholarly field by about two centuries. Broadly conceived histories of science and medicine were being written in the eighteenth century, when such an all-encompassing vision was central to the claims about the progress of knowledge upon which Enlightenment ideologues set such store. The Plato to Nato style histories, characteristic of the earlier twentieth century, were written largely by isolated pioneers, and while these were used in teaching as the field was becoming professionalized, recent scholars have preferred to concentrate on a monographic style of research. Despite the existence of the series started by Wiley, and now published by Cambridge University Press, it is only in the last ten years or so that more conscious attempts have been made to generate a big-picture literature informed by new scholarship. It is noteworthy that most of this is addressed to students and general readers, although there is no logical reason why it should not tackle major theoretical issues of concern to scholars. My point about maturity still holds, then, since as a designated discipline the history of science is rather new; it is still feeling out its relationship with cognate disciplines. Big-picture histories have an important role to play in these explorations since they make findings and ideas widely available and thereby offer material through which ambitious interpretations can be debated, modified and transformed.