This book provides a systematic presentation of issues pertaining to the development of dichroic dyes applied in electrooptical systems for displaying and processing data. It explains the theory of the guest-host effect and the methodology of engineering dichroic dye (DD) molecules with specified characteristics. The book then examines the properties of currently known DDs, including the most interesting examples of synthesis. Various aspects of designing LCM for guest-host devices and available designs of guest-host LCDs are considered as well. Characteristics of dichroic dyes are presented in the Appendix as an added benefit to readers.