Zeolites and zeolite-like materials became important because of their ion exchange capacities and their outstanding catalytic properties. Millions of tons of zeolites have been produced in the past years for the oil refining industry alone and, in even greater quantities, as ion-exchanging softening agents for detergents. Numerous other applications, e.g., in environmental protection, farming, gas separation, medicine, and pharmacy, are known, making zeolites almost a necessity for daily life. Consequently, there are many research activities dealing with zeolite properties and characterization. However, a strictly systematic description of zeolite-type crystal structures was not available but is now presented in this series of volumes. It is designed as a reference work for zeolite chemists and materials scientists, but it also serves as a tool to interpret structural similarities and to derive new structures from known topologies.