The book is devoted to the achievements of two complementary multispacecraft missions – INTERBALL and CLUSTER II. The advantages of these powerful instruments for magnetospheric investigations are clearly shown together with problems that were or should be overcome in the mission management and data processing and interpretation. The main goal of both missions is the investigation of coupling among different magnetospheric regions and, consequently, the core of the book deals with this topic. Nevertheless, various coupling processes are influenced by upstream conditions or triggered by solar wind or interplanetary magnetic field disturbances. The book also stresses the importance of the solar wind input on magnetospheric processes. The Editors of the book hope that it will be useful for scientists involved in Solar– Terrestrial relations or Space Weather programs as well as for students of space or plasma physics. The book surveys present knowledge and puts it into context of the latest results of aforementioned missions. Since the book treats not only achievements but the problems of multispacecraft observations as well, it can serve as a tool for the planning of further missions.