Porous materials generally refer to solids that contain pores in their structure. One of the most important concepts studied in porous materials is porosity. Porosity is obtained by dividing the volume of cavities by the total volume of the material. Porous materials have attracted the attention of scientists due to their various applications in molecular separation, heterogeneous catalysis, absorption technology, or light and electronics technology. In general, the surface area of porous material is higher than its non-porous material. The cavities in porous materials are divided into two types of open cavities and closed cavities. Open cavities have access to the surface of matter, but closed cavities are trapped within matter. In basic applications such as catalytic processes, separation and filtration, open cavities play an essential role. But the most important applications of closed cavities include the manufacture of thermal, acoustic and low-density devices. Join us on a short journey to the depths of the pores of porous materials!