We demonstrate the achievments of the ISTP program using two well-studied events as examples and discuss the outstanding issues pertinent to the Cluster II program. The studies of a substorm on May 15. 1996, among many other substorm studies, have revealed the systematic spatial and temporal sequence of the global substorm. We emphasize the open questions related to mesoscale objects such as thin current sheets, bursty bulk flows, localized flow channels. and the reconnection region, and demonstrate the capabilities of the Cluster mission to address these topics. A well-studied storm event on May 15, 1997, is an example of storms during which strong and rapid relativistic electron acceleration occurred deep in the inner magnetosphere. We list some of the open issues related to the particle acceleration, and discuss the fortuituous orbit of Cluster II to examine such processes.