Mass-radius diagram for all planets with radii R < 4 R_⊕ characterised by HARPS-N (coloured dots, with the colour scale based on the precision of mass measurement). Non-coloured dots correspond to all other planets with R < 4 R_⊕ and a mass precision higher than 30% as measured by means of RVs. The three transiting planets orbiting HD 224018 are indicated with green squares. Green dots indicate the location of Earth and Venus. Some compositional theoretical curves are also plotted (Zeng et al. 2019).