The developing field of molecular electronics has come to encompass many types of molecular electronic devices, including polymer-based light-emitting-diode (LED) displays, solar energy conversion devices, and a variety of chemical sensors. A characteristic feature of most molecular electronic devices is that they involve an intimate coupling of molecular materials with conventional solid-state electronic materials. A very promising subdiscipline within the field of molecular electronics involves the use of individual molecules or molecular aggregates in place of solid-state materials as active elements in circuits designed to accomplish logic functions. Such circuits are being considered as possible building blocks for futuristic molecule-based computing devices. A great attraction of such devices is the potential for miniaturizing computing devices, thereby increasing their power and enabling entirely new applications.