On the basis of data available in the literature and the experimental results obtained by the authors, general developmental trends in studying the chemistry of microporous and mesoporous molecular sieves are discussed. The most important lines and objects of research were outlined, in particular, template synthesis of extra-large pore zeolites (silicates, germinates, phosphates, etc.) and mesoporous molecular sieves (MMS) of various types and compositions based on Si, Al, Ti, Zr, Ge, Sn, and some transition metal oxides and phosphates, as well as carbon MMS. Some of the current approaches and new ideas and approaches to the structuring and functionalizing of molecular sieves related to the chemistry of the template action; the specifics of isomorphism of the template action in phosphate and germanate zeolite-forming systems, as well as in MMS; the solubilization effect, etc. are considered.