Chromatography method in which a gaseous, liquid or supercritical mobile phase containing species to be separated is circulated through a packing, said packing being characterized in that: —it comprises a plurality of capillary ducts extending in the packing between an upstream face through which the mobile phase enters the packing and a downstream face through which the mobile phase leaves the packing—the material of the walls comprises a first population of connected pores, providing passages from one duct to the next enabling molecular diffusion to take place between adjacent ducts, pores having a mean diameter (dpore) of greater than 2 times the molecular diameter of at least one species to be separated—the diameter of the ducts is less than 50 μm.