Crystalline porous materials, such as zeolites and metal-organic frameworks (MOFs), possess a regular and well-defined system of pores. While zeolites have been known for a long time and are widely used in industry, MOFs are still a new type of compounds with a huge potential for numerous applications. MOFs and zeolites may feature certain similarities as well as large differences, but concepts such as flexibility of the framework, thermodynamic versus kinetic control of the crystallization or stabilizing effect of guest species are key issues in both fields. This article presents a vision on the state of the art of such materials.