Planetary masses and radii (main panel), and histogram of the masses (top panel) and radii (right panel) of the known transiting exoplanets (TepCat catalog, Southworth 2011) with equilibrium temperature T_eq evaluated between 600 and 1000 K. The composition models of hydrogen-, ice-, silicate-, and Fe-metal-rich planets (solid colored lines) are computed from Seager et al. (2007), Zeng & Sasselov (2013), and Becker et al. (2014) (see details in Sect. 5.2). The dashed lines show the composition models with a relatively cold hydrogen envelope of mass fractions of 10, 20, 30, and 50%. The Solar System planets are shown as gray dots.