In this video we show the process of gas adsorption during the measurement of gas adsorption / desorption isotherms. We present the process of adsorption as the isotherm is collected, showing regions of the isotherm that relate to micropores, mesopores and macropores, as well as the BET surface area. Finally, we show the derivation of micropore size data using DFT and mesopore / macropore data using BJH methods.