The characterization of the physico-chemical properties of high-pressure and high-temperature C-H systems is of great importance in many fields such as organic, bio and petroleum chemistry as well as in planetary science. Methane in particular is a crucial molecular species whose phase diagram has been predicted up to 300 GPa but only studied through X-ray diffraction up to 200 GPa. We aim to reach pressures above 400 GPa using toroidal diamond anvils. Obtaining X-ray diffraction data in the 200-450 GPa range will let us determine the methane equation of state, study its intrinsic stability, and obtain useful data for comparison with planetary interiors models. Additional laser heating performed at various pressures will let us explore its pressure-temperature phase diagram and study its chemistry.