A supercritical fluid is a state of matter that occurs when a substance is heated and pressurized beyond its critical point. In this state, the fluid exhibits properties of both a liquid and a gas, allowing it to diffuse through solids like a gas while dissolving materials like a liquid. This unique behavior makes supercritical fluids useful in various applications, including extraction and chromatography. One of the most common supercritical fluids is carbon dioxide, which is often used in supercritical fluid extraction to obtain essential oils and flavors from plants. This method is favored for being environmentally friendly and efficient, as it avoids the use of harmful solvents.