Supercritical fluids are substances that exist at a temperature and pressure above their critical point, where distinct liquid and gas phases do not exist. In this state, they exhibit unique properties, such as the ability to dissolve materials like a liquid while also diffusing like a gas. This makes them useful in various applications, including extraction processes and chemical reactions. One common example of a supercritical fluid is carbon dioxide, which is often used in supercritical fluid extraction to obtain essential oils and flavors from plants. The ability to fine-tune the temperature and pressure allows for selective extraction, making it an environmentally friendly alternative to traditional solvents.