A new class of microfiltration membrane nuclear filters is described. The facts are presented concerning the features of nuclear filter pore structures that give them the advantages of traditional sieve membranes. The structure, physical properties and applications of nuclear filters, in particular in modelling of reverse osmosis processes and in efficient separation of colloidal solutions and crystallization media, are discussed. Data are also included on the applications of nuclear filters which are unusual by comparison with the applications of conventional membranes: the synthesis of secondary structures-pointed-top (protruding) structures, porous metallic replicas, etc. and properties of such secondary structures.