The radiocarbon dating technique, which measures the decay of the carbon-14 (${}^{14}\text{C}$) isotope, is primarily used to estimate the age of:

Radiocarbon dating is an archeological and biological tool used to determine the age of organic matter up to roughly $50,000$ years old. Since fossils, wood, bones, and shells retain organic carbon residues from living entities, their age can be measured via ongoing beta-decay tracking of carbon-14. Inorganic objects like deep geological rock strata require uranium-lead or potassium-argon dating methods.