  In its original formulation, the seminal Deryaguin-Landau-Verwey-Overbeek
(DLVO) theory of colloidal stability seemed like a simple but realistic
description of the world of colloid interactions in electrolyte solutions. It
is based on a straightforward superposition of the mean-field Poisson-Boltzmann
(PB) electrostatics with the electrodynamic van der Waals (vdW) interactions
driven by thermal and quantum fluctuations. However, subsequent developments
continued to reveal a much richer and deeper structure of fundamental
interactions on the nano- and micro-scale: the granularity and structure of the
solvent, charging equilibria of dissociable charge groups, inhomogeneous charge
distributions, the finite size of the ions, non-mean-field electrostatics,
ion-ion correlations, and more. Today, the original simplicity is gone and we
are left with an embarrassingly rich variety of interactions that defy simple
classification and reduction to a few fundamental mechanisms. In this
mini-review, we comment on the contemporary state-of-the-art picture of
colloidal interactions, in view of some recent progress in experiments.
