Offering a materials science point of view, the author covers the theory and practice of adsorption and diffusion applied to gases in microporous crystalline, mesoporous ordered, and micro/mesoporous amorphous materials. Examples used include microporous and mesoporous molecular sieves, amorphous silica, and alumina and active carbons, akaganeites, prussian blue analogues, metal organic frameworks and covalent organic frameworks. The use of single component adsorption, diffusion in the characterization of the adsorbent surface, pore volume, pore size distribution, and the study of the parameters characterizing single component transport processes in porous materials are detailed.