Chemical vapor deposition starts with a diamond seed, a hydrocarbon gas, and hydrogen in a vacuum chamber. Through this process and over many steps, the temperature in the chamber is raised to 900° to 1200° C. Meanwhile, the gas mixture (reacting throughout the process) becomes a highly reactive carbon-hydrogen species. At the point when the temperature is raised, it travels across the diamond 'seed' and deposits diamond material atom-by-atom, almost endlessly, again and again, until the crystal structure of the diamond is grown.