Metamorphism is the process by which existing rocks, known as parent rocks or protoliths, are transformed into new types of rocks called metamorphic rocks. This transformation occurs due to changes in temperature, pressure, and the presence of chemically active fluids over long periods of time. During metamorphism, the minerals within the parent rock may recrystallize, change in composition, or align in a new structure, resulting in distinct textures and properties. Common examples of metamorphic rocks include schist, gneiss, and marble, each formed under specific conditions of heat and pressure.