With the development of new synthetic methods, semiconductor nanocrystals of various morphologies and dimensions have been created. This changes their electro-optical properties, and brings new questions in understanding. At the same time, more and more research is now focused on nanocrystal assemblies, in particular nanocrystal superlattices with atomically coherent lattices, with the potential for various optoelectronic device applications. This thesis examines, in both theory and experiment, a number of nanocrystal systems, with the stress on dimensionality and morphology. In particular, in 1D and 2D systems, due to the anisotropic quantum confinement, the electrons and holes will form a tightly bond excitons, even at room temperature, in contrast to 0D and 3D systems, where either quantum confinement or coulomb interaction completely dominates. We'll also look into nanocrystal assemblies, both amor- phous and atomically coherent, and study the effect of the inherent disorder in the structure on their electronic properties, with the goal of charge transportation through delocalized states. nanocrystals. Last, we'll examine the fine structure in these