Luminescence dating, particularly using optically stimulated luminescence (OSL), is revolutionizing Quaternary and archaeological science because it allows dating of sediments and artifacts that perhaps 10 years ago could not be dated. As the OSL of a sediment is quickly lost when exposed to sunlight (tens of seconds) many sediments are bleached (lack an OSL signal) when deposited and buried. After deposition these sediments accumulate luminescence which can be measured allowing the age of burial to be determined. There is now convincing evidence that many glacial, fluvial, aeolian, and even shallow marine sediments can be dated by OSL techniques. The upper limit of age by OSL is largely determined by the annual dose on the sediment which is related to it's content of uranium, thorium and potassium. Low levels of radioactive isotopes in the sediment lead to very slow saturation of quartz and feldspar grains by released electrons and so ages in excess of 500 ka may be possible. Typically OSL techniques produce ages from one or two hundred years to about 400 ka with an error of around 10%.