Empirical relations that describe the dependence of the atmospheric composition in exoplanets from their escape velocities and equilibrium temperatures. The plot show the location of the K2-36 planets in the context of some notable small-size exoplanets (R < 4 R_⊕) with measured masses (K-: Kepler planets; T-1: Trappist-1 planets). A colour code is used to distinguish the planets on the basis of their bulk density.