A Grid provides unlimited virtual resources to users without revealing the internal structure. Like in real markets, the resource limitation should not be noticed by customers. The combination of all demands and all available resources is performed by market mechanisms. This is the overall goal of Business in the Grid for virtual resources, the economic and transparent utilization of virtual resources. We enabled doing business by establishing the homogeneous access to virtual resources without revealing the heterogeneous and dynamic manner of the underlying real world. The fulfillment of this promise highly depends on the user's requirements. An ideal virtual resource is independent of its real properties and corresponds perfectly to the user's requirements. To make Business in the Grid possible the ad-hoc, dynamic access to any virtual resource combined with authorization, trust, privacy and inherent accounting mechanisms are key challenges. The author of this book details the challenges and provides solutions to these issues.