Any classification into types can clarify our view of the whole while, at the same time, distracting our attention from hybrids and the processes by which they are formed and sustained.1 In this light, the recent review by Sismondo, which teases out some of the multiple meanings given to the term 'construction', and his subsequent exchange with Knorr-Cetina,2 should leave us troubled. Many of us are interested in the processes of science in the making, in which scientific theories, materials, tools, language, institutions and wider social relations are being co-constructed, and are trying to analyze the diverse 'resources' drawn upon by agents in such co-construction processes.3 Sismondo's classification makes little space for that strand of social studies of science, focusing as it does on the type of thing being produced, not the processes of their production. Knorr-Cetina does not take issue