The e-PYTHEAS project sits on the frontier between molecular physics, theoretical chemistry and astrophysics. It aims at enhancing our understanding of the radiative properties of hot gaseous media to allow for improved analysis and interpretation of the large mass of data available on the thousands of exoplanets and exoplanetary systems known to date. Our multidisciplinary approach – theoretical research validated by laboratory experiments and injected into models of the atmospheres of the giant  gaseous planets – will help to address essential questions on the formation and evolution of planetary systems.