This book covers a wide range of topics related to functional dyes, from synthesis and functionality to application. Making a survey of recent progress in functional dye chemistry, it provides an opportunity not only to understand the structure-property relationships of a variety of functional dyes but also to know how they are applied in practical use, from electronic devices to biochemical analyses. From classic dyes such as cyanines, squaraines, porphyrins, phthalocyanines, and others to the newest functional π-conjugation systems, various types of functional dyes are dealt with extensively in the book, focusing especially on the state of the art and the future. Readers will benefit greatly from the scientific context in which organic dyes and pigments are comprehensively explained on the basis of chemistry.