The focus of the work is on phenomena, in which chemical reactions are coupled with diffusion and the book presents fundamental aspects of reactiondiffusion with its applications in modern small-scale technologies. The book begins with a historical perspective and outlook for reaction-diffusion (RD) systems as well as a description of how nature uses RD and RD in science and technology. Chapters 2 and 3 deal with the basic ingredients: diffusion and chemical reactions, respectively. Reaction-diffusion equations and the methods of solving them are tackled in Chapter 4. In Chapters 5 to 7, spatial control of reaction-diffusion at small scales, fabrication by reaction-diffusion and multitasking are covered. Chapter 8 is concerned with reaction-diffusion at interfaces. The concluding chapters  concern reaction-diffusion for amplification and sensing and RD in three dimensions and at the nanoscale and are followed by three appendices. Ultimately the book guides the reader through all the aspects of these systems from understanding the basics to practical hints and then how to interpret its results.