Abstract <p>The Micro-Thermal Field-Flow Fractionation (<b>Micro-TFFF</b>) was proposed and continuously developed for the analytical separations of macromolecular and particulate species of synthetic, natural and biological origin. The progress in theory of the separation mechanisms of Micro-TFFF inspired the improvement of the experimental methodology and instrumentation. On the other hand, the important progress in construction of more powerful apparatuses permitted to attain the performance of analytical separations close to the predicted theoretical limits. Surface properties of colloidal particles, exposed to the temperature gradient, influence fundamentally their migration. The spherical particles of identical size but of different surface properties migrate in temperature gradient differently. The shape and surface topographical heterogeneity of the particles also distinguish their thermal diffusion. It was anticipated and theoretically calculated that the separations of the colloidal particles based on the mentioned particular differences could be possible by using Micro-TFFF. The theoretical conclusions were confirmed by real separations of various particulate species including living bacteria cells.|</p>