Very recently superconductivity near Tc ~ 80 K in La3Ni2O7 was reported above P* = 14 GPa at proximity of a structural transition from Amam to Fmmm space groups at 300 K. The aim of this proposal is to clarify the relationship between superconductivity and this structural transition by performing an XRD study of La¬ 327 powder under pressure and from 300K down to 5K to check the crystal structure of the superconducting phase. The use of a better hydrostatic PTM (neon or helium) than in the previous studies (oil or solid media) will allow an accurate determination of the full P,T phase diagram.