Abstract Development of membranes resistant to heating and chemicals is expected for the separation of small molecules in biotechnologies, pharmaceutics, chemical industries, water treatment and also in gas separation. When aiming at separation of small molecules (molar mass less than 1000) or multivalent ions, nanoscale pores or almost dense materials will be required. Pure inorganic materials as well as organic/inorganic polymers are very good candidates for preparing this new generation of membranes. The nanostructural organization of sol—gel derived materials means that the sieve concept developed for microfiltration (MF) and ultrafiltration (UF) membranes can be surpassed and an “intelligent membrane” concept can be recognized for nanofiltration membranes. In fact, specific interactions are expected between the nanophased membranes and solubilized species or gas molecules passing through the membrane. Provided that these interactions can be managed, an increase in membrane performances is obtained, with the possibility of developing new application fields. Examples are given showing the important role played by the basic properties of ceramics and organically modified ceramics in the production of tailored nanofiltration membranes.