In every stage of experiment in low temperature physics and cryogenic engineering liquid helium and nitrogen are used popularly, but they are not necessarily used properly. The proper usage of these cryogen is reconsidered in this article by investigating the thermophysical property differences in latent heat, thermal conductivity, enthalpy and so on. To make your own cryogenic “map” based on thermophysical properties compared with other cryogen as hydrogen and oxygen would be the key to solve troubles encountered in your experiment.