Zeolites represent an important class of materials exhibiting a well-defined hydrothermally stable framework with pores of molecular dimensions 0.3-1.5 nm. One of the main drawbacks arising in catalytic applications concerns the limited molecular transport in these micropores, and it has been demonstrated that mass transfer limitations restrict the extent of catalytic conversions over zeolites. To circumvent this, since 1992, ordered mesoporous materials have widely attracted the attention of scientists in view of improved transport in the pores covering the lower nanometer-size range. The overall relatively poor (hydro)thermal stability, lack of (strong) acidity, and absence of confinement effects have, however, resulted in limited practical applications. Given this situation, materials exhibiting a hierarchical architecture of porosity are gaining increased interest. The larger pores facilitate physical transport, whereas each micropore acts as a nanoreactor providing active sites and shape selectivity. Hydrothermal treatment and/or acid leaching are classical post-synthesis approaches in research labs and industry to induce mesoporosity in acidic zeolites. An innovative methodology is desilication, a post-synthesis modification treatment in which, contrarily to the well-known dealumination treatment, silicon is selectively extracted from the zeolite framework. In my talk, the first example is given on desilication in alkaline medium of large ZSM-5 crystals presenting a homogeneous distribution of framework aluminum, leading to an accessible interconnected network of intracrystalline mesopores and preserved crystallinity. The second example is taken on the application of meso-Fe-ZSM-5 to the direct catalytic oxidation of benzene to phenol by N 2 O. The last example is given on the isomerization of normal hexane over Pt/meso-MOR and Pt/meso-ZSM-12.