This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.This paper concerns the ways in which futures are enacted, and thus mobilized, by publics, participants and practitioners, and especially by social scientists. In particular, the paper is interested in the assortment of futures within which we are seemingly embroiled, and how we analytically deal with the proliferation of futures. This is approached through the dramatization of futures as ‘Big’ or ‘Little’ in which change is more or less wide-spread and far-reaching. The aim is to chart some of the ways in which Big Futures are analytically or rhetorically transformed into Little and vice versa, and thus to throw into relief the mutability of futures per se. This discussion is developed by drawing on a particular area of social scientific inquiry, namely the ‘Public Understanding of Science’ (PUS) which also includes the field of ‘Public Engagement with Science and Technology’ (PEST). The role for Big Futures (indexed by ‘controversiality’) in this field, and the Big Future claims made by PUS/PEST practitioners are contrasted to the Little Futures of everyday life. With the aid of a ‘speculative’ sensibility, Little Futures are then shown to be potential sources of Big Futures. The paper ends with a preliminary attempt to theorize the complex interactions of Big and Little Futures through Isabelle Stengers’ (2010) notion of an ‘ecology of practices’.