D. functional theory (DFT) has progressively emerged in the last 40 years as a leading methodol. for the modeling and simulation of chem. systems. In this paper, some historical landmarks in the development of this method are outlined, emphasizing on its main characteristic being an electron d.-based theory. This is in contrast with wavefunction-based methodologies which were exclusively employed previously. Interestingly, DFT has been first applied to solids, with a rather late recognition by chemists and mol. scientists. After this historical survey, several applications of DFT to the structure and properties of zeolites are reviewed as a tribute to Dr Annick Goursot. [on SciFinder (R)]