We investigate the stability and dissociation of methane,which is the most abundant organic molecule in the universe,using diamond anvil cell(DAC)with in situ Raman spectroscopy up to 903K and 21GPa.At the temperatures of 793 and 723K and the corresponding pressures of 16.15 and 20.30 GPa,methane dissociates to very high,methane remains stability up to the highest temperature of 903 K of the work.The four symmetricC-H bonds of methane split at high temperatures and at high pressures,and there is at least one phase transitionof crystalline symmetry from face centred cubic (fce) to hexagonal dose packed (hcp) before dissociation.