The activity of Prof. Eric G. Derouane expanded over numerous directions in zeolite chemistry, from the development of pioneering physical concepts to the optimization of chemical synthesis, including catalysis. His ideas were an inspiring basis of many modern experimental and theoretical studies for many researchers at the University of Namur. In this University, where Eric has been Full Professor for over 20 years, all of us have benefited from Eric's friendship and from numerous frequent and fruitful discussions in the zeolite domain. D.P.V. is particularly indebted to Eric's long term vision regarding the multiple aspects to tackle using molecular simulations of sieves in general. With this paper, we wish to honor Eric's memory by recalling the pioneering physical concepts of confinement which have influenced more than 20 years of theoretical simulations of molecular sieves. We will also briefly mention the on-going theoretical work towards template design for the syntheses of porous materials.