Mass-radius diagram for exoplanets with both mass and radius known with a relative precision better than 30% (gray points). AU Mic b and c are shown with red circles and error bars. Theoretical models from Zeng et al. (2019) for various inner planet structures and compositions are depicted with a solid black line (100% iron and Earth-like) and blue line (50% water envelope). Models from Aguichine et al. (2021) for a 50% water envelope including the effects of irradiation, are plotted as a solid green line. Models with a 1,2 and 5% H₂ atmosphere with either an Earth-like (dashed brown lines) or a 50% water (orange dashed line) interior are also shown. Dashed grey lines indicate iso-densities of 1,3, and 10 g cm⁻³ (from top to bottom).