How does science create knowledge? Epistemic cultures, shaped by affinity, necessity and historical coincidence, determine how people know and what they know. This text compares two epistemic cultures, those in high energy physics and molecular biology. It highlights the diversity of these cultures of knowing and, in its depiction of their differences - in the meaning of the empirical, the enactment of object relations, and the fashioning of social relations - challenges the accepted view of unified science. Comtemporary Western societies are becoming "knowledge societies", which run on expert processes and systems epitomized by science and structured into all areas of social life. This work addresses questions about how such expert systems and processes work, what principles inform their cognitive and procedural orientations and whether their organization, structures and operations can be extended to other forms of social order.