The maturity of a source rock refers to its state (degree of thermal alteration) in terms of hydrocarbon generation potential. Maturity is assessed using vitrinite reflectance (%Ro), Tmax (from Rock-Eval pyrolysis), or thermal alteration index (TAI). Immature rocks have not generated hydrocarbons; mature rocks are in the oil window (~0.6–1.3% Ro); overmature rocks have generated dry gas or are spent.