The aim of this book is to acquaint the reader with what the authors regard as the most basic characteristics of quasicrystals -- structure, formation and stability, and properties -- in relationship with the applications of quasicrystalline materials.Quasicrystals are fascinating substances that form a family of specific structures with strange physical, chemical and mechanical properties as compared to those of metallic alloys. This, on the one hand, requires a generalization of the crystallographic description of solids and is still stimulating intensive research to understand the most basic properties of quasicrystals. On the other hand, these properties open the way to technological applications, demonstrated or potential, mostly regarding energy savings.This valuable book discusses those various facets of quasicrystals in six chapters, ending with the authors' own interpretation of the properties with respect to their unique structure.