Résumé : I will present the results of new 3-D Global Climate Model (GCM) simulations aimed at reproducing the conditions of primordial surface water condensation and thus of the formation of oceans on terrestrial planets. The simulations reveal that clouds preferentially form on the nightside of young and hot telluric planets endowed with a water-rich atmosphere. These clouds thus have a net warming effect that effectively prevents the formation of surface liquid water oceans. I will show how this result has important implications for the past and present habitability of Earth and Venus. I will also discuss this result in the context of Mars. Finally, I will present the implications for exoplanets, and discuss ways to test this result observationally, in particular with the support of JWST (James Webb Space Telescope) observations.