There are 2 technologies for simulating the formation of a diamond. The first technique is the HPHT (high pressure, high temperature) process, the second is CVD (chemical vapor deposition). HPHT simulates the conditions inside the Earth's crust, allowing lab-created diamond to grow under intense heat of 1200-1500°C and high pressure. Using the CVD technique, laboratory-created diamond is grown in a vacuum chamber by adding methane and hydrogen at temperatures of 700–900 °C.