The aim of this book is to acquaint the reader with what the author regards as the most basic characteristics of quasicrystals -- structure, formation and stability, properties -- in relationship with the applications of quasicrystalline materials.Quasicrystals are fascinating substances that form a family of specific structures with strange physical and mechanical properties as compared to those of metallic alloys. This, on the one hand, is stimulating intensive research to understand the most basic properties of quasicrystals in the frame of a generalized crystallography. 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 five chapters, ending with the author's own interpretation of the properties with respect to their unique structure.