HPC 900 is a unique high-pressure and high-temperature chamber for in-situ X-ray diffraction studies of gas-solid interactions. HPC 900 can be pressurized with hydrogen and many other gases up to 100 bar while heating the sample up to 900 °C. A furnace heater provides uniform sample heating and excellent temperature control. Despite the extreme operating conditions, the sample can be exchanged easily without any tools. HPC 900 opens up completely new possibilities in hydrogen energy research and catalyst development.