As microporous materials, zeolites entrap molecules allowing their diffusion, adsorption and reaction within the channel system. This confinement affects the physico-chemistry Of Such incoming molecules in different ways. Derouane pioneered research onto the confinement effect in zeolites and extracted ideas and conclusions regarding physisorption, catalytic cracking and diffusion. His work on this topic is reviewed in this article and further updates on the confinement effects by other groups are also analysed. (c) 2008 Elsevier B.V. All rights reserved.