In this thesis we focus on the structural refinements present in the associated liquids. Using the molecular dynamics simulations we probe the microstructure of these liquids, namely the neat systems and alcohol-water mixtures. From the correlation functions in direct and reciprocal space and as well as the cluster distribution functions we create a consistent picture of the structural specificity that exist in the associated liquids. We made a distinction between the structural organization in pure liquids and in binary systems, first defined through the local self-association of molecules, and second corresponding to a local segregation of the components of the binary system. In each case the highly anisotropic site-site hydrogen bonding has main role. In the pure liquids the association is induced through specific site-interactions that lead to an inhomogeneous distribution ofsites, while the molecular distribution preserves the liquid-like behavior. In the binary system the micro-heterogeneity is due to the local immiscibility of the species. Micro-heterogeneity appears to be universal feature of aqueous solutions, predominantly driven by hydrogen bonding. Micro-heterogeneous order does not quite fit in the class of disorder, but neither in that of order. It appears like a new form or order, and challenges our techniques to put this in evidence, both experimentally or through simulations.
