The book investigates QDs and SWCNTs using quantum-chemical calculations that describe intricate details of excited-state phenomena and provides information about the mechanisms that occur on the atomic level and that are extremely difficult, if not impossible, to probe experimentally. It delivers, consistently and coherently, a novel approach to nanomaterials which is promising for today's technologies as well as their future. This approach elegantly overcomes computational difficulties known in the field and shares ways to reach top performance in the description of combined quantum effects of molecular vibrations and exciton formation on realistic-size numerical models. The reader will acquire an understanding of the pioneering methodology supported by most recent original results, prospectively applicable to the design of new nano-devices.