This book provides concepts and experimental demonstrations for various types of molecular layer deposition (MLD) and organic multiple quantum dots (organic MQDs), which are typical tailored organic thin-film materials. Possible applications of MLD to optical interconnects, energy conversion systems, molecular targeted drug delivery, and cancer therapy are also proposed. First, the author reviews various types of MLD processes including vapor-phase MLD, liquid-phase MLD, and selective MLD. Next, he introduces organic MQDs, which are typical tailored organic thin-film materials produced by MLD. The author then describes the design of light modulators/optical switches, predicts their performance, and discusses impacts of the organic MQDs on them. He then also discusses impacts of the organic MQDs on optical interconnects within computers and on optical switching systems. Finally, the author presents MLD applications to molecular targeted drug delivery, photodynamic therapy, and laser surgery for cancer therapy. This book is intended for researchers, engineers, and graduate students in optoelectronics, photonics, and any other field where organic thin-film materials can be applied.