Labels are important to the emergence of organizational fields. The construction and use of labels enables communication and coordination across communities. This paper argues that new and existing communities’ uses of labels commence a categorization process central to the construction of meaning and definition of boundaries within organizational fields. Employing 25 ethnographic observations, 77 interviews and 12,774 articles from five different nanotechnology communities covering primarily the 21 year period from 1984 to 2005 I show the differentiated use of the nanotechnology label across communities. Scientists and entrepreneurs were not the creators and first adopters of the nanotechnology label, instead futurists, the government and venture capitalists played pivotal roles in promoting the nanotechnology label by supplying the field with resources and infusing the nanotechnology label with meaning. Theoretically this paper adds to our understanding of field emergence by reframing emergence as a categorization process.