The discovery of conducting polymers opened up many new possibilities for devices combining unique optical, electrical, and mechanical properties. The literature on conducting polymers as reflected in its top-cited papers shows the diversity of materials that can be used, optical effects achieved, and underlying physical processes. The substances include organic polymers, copolymers, and conjugated polymers, such as poly(para-phenylene), polyaniline, and poly(p-phenylenevinylene). These can be fabricated to have high flexibility. The devices are mainly light-emitting diodes (LEDs), or, more recently, lasers, and the color of the light emitted can be chemically tuned. The main physical process involved is electroluminescence. The conducting polymers can be induced to transfer electrons to other materials such as Buckminsterfullerene. Inorganic materials can also be used to create LEDs, such as InGaN materials, or cadmium selenide nanocrystals, where t he physical process involves quantum-wells.