With the collapse of the planned economies of Eastern Europe, the market is extending its reach and at the same time claiming its universal applicability. But this is occurring while paradoxically it is becoming more difficult to define "the market". The authors, all outstanding scholars in the booming field of socio-economics, explore how concrete markets are built up and stabilized. They give answers to questions such as the following: How are entities, material or non material, human or non human, transformed into commodities? How are economic behaviours shaped by institutional arrangements? Is it possible to characterize the role of the social sciences and in particular of economics in performing markets and in enforcing rational behaviours?