In the course of the six centuries and more considered here, the concept of the naturalist and of the work that he or she undertakes in the field gradually took form and continues to develop. The status of the practitioners involved is so widely disparate as to defy easy categorization. In these introductory remarks some of the principal communities – arbitrarily defined – contributing to this movement are reviewed: a number of the most significant figures emerged from within the academic milieu, conducting their work initially in the tradition of the classical authors whose tracts held sway until the late Renaissance, yet they were increasingly reliant on the ocular evidence on which the New Science was built; others came from outside this tradition but contributed invaluable personal experience, insight and knowledge, practically acquired. Both are celebrated here, and their mutually enriching relationships are explored. Other essays here adopt a more specific focus in order to chart the ways in which the field practice that lies at the heart of this volume was guided and influenced by those who commissioned collecting expeditions – initially the founders of collectors’ cabinets, later the owners of systematic collections and ultimately the curators of veritable natural history museums. All of these operated in the role of sponsors for the field naturalists and all were anxious that material should reach them not only in optimum condition but with appropriate contextual data. Their demands were communicated variously in the course of correspondence, in printed pamphlets and ultimately in book-length instructions published for the benefit of those in the field: some of these texts are reproduced verbatim as appendices at the end of the volume.