High-pressure physics is concerned with the effects of high pressure on the properties of matter. Since most properties of matter are modified by pressure, the field of high-pressure physics encompasses virtually all branches of physics. The justification for classifying high-pressure physics as a separate field is that rather specialized and often ingenious techniques are needed, both to produce high pressures and to make measurements of changes of physical properties of a material at high pressure. This field is therefore analogous to the fields of low- and high-temperature physics. Indeed, high-pressure experiments have been performed at temperatures approaching absolute zero and at temperatures as high as 9000°F (5000°C).