1 Introduction Due to of similarities between the Schrodinger equation and the Maxwell's equations,the concept of electronic structure methods can be adopted for the study of photonic nano-materials,which have important applications in micro-and nano-electronics.Such computer simulations help to understand quantum dots or photonic crystals that act as new source of a coherent radi- ation,cages or guided pathways,operating on smaller and smaller scales at steadily increasing speed. In this book the above-mentioned aspects of computational physics will be discussed from frameworks to practical applications.The general orga- nization of this book is as follows (see the table of Contents).Part I gives a basic description of electrons and photons in crystals.Part II reviews the various techniques of simulations of nanoscopic and macroscopic materials. Some practical aspects of parallel computing and multi-grid methods will be presented in Part III.The interested reader can find references of several other works in the bibliography sections at the end of each chapter.1 Introduction 3 Due to of similarities between the Schr¨odinger equation and the Maxwell’s equations, the concept of electronic structure methods can be adopted for the study of photonic nano-materials, which have important applications in micro- and nano-electronics. Such computer simulations help to understand quantum dots or photonic crystals that act as new source of a coherent radi￾ation, cages or guided pathways, operating on smaller and smaller scales at steadily increasing speed. In this book the above-mentioned aspects of computational physics will be discussed from frameworks to practical applications. The general orga￾nization of this book is as follows (see the table of Contents). Part I gives a basic description of electrons and photons in crystals. Part II reviews the various techniques of simulations of nanoscopic and macroscopic materials. Some practical aspects of parallel computing and multi-grid methods will be presented in Part III. The interested reader can find references of several other works in the bibliography sections at the end of each chapter