All materials possess interat. or interionic voids that are typically too small for any mol. species to enter. However, there is a class of cryst. materials that contain internal voids, and apertures, that are large enough for mol. species to enter and pass through. These materials are termed microporous and form a highly diverse group of compds. that may be synthesized or occur as natural minerals. The compn. of microporous materials ranges from being exclusively inorg. to inorg.-org. hybrids and their applications vary from 1 Mton annual usage in detergents, to hosts for superconducting carbon nanotubes. In this contribution, new and mature aspects of the synthesis, scope, modification and application of microporous materials are covered to provide the reader with an overview of this exciting field of materials chem.