on-specific effects are ubiquitous in nature and have relevance in colloidal science, electrochemistry, and geological and biological physics. The molecular origin and the coarse-grained modeling of these effects are still widely unexplored. In this talk we attempt to give more molecular insight into the individual correlations in aqueous electrolyte systems which give rise to the ion-specific behavior in bulk (e.g., the osmotic pressure) or in confinement (e.g., between colloidal or biological surfaces). Particularly, we present a nonlocal Poisson-Boltzmann theory, based on classical density functional theory, which captures and rationalizes ion-specific excluded-volume correlations (the 'size effect') in dense electrolytes and may help understanding the restabilization of proteins, clays, and colloids at high salt concentrations. The importance of electrostatic correlations at low dielectric constants is briefly discussed.