By BBC Scotland science correspondent Kenneth Macdonald
The key to the dating process is an isotope - a variant - of carbon.
Carbon-14 is that element's only radioactive isotope and every piece of organic material - ourselves included - contains a tiny amount of it.
Its relatively slow rate of radioactive decay means it has a half-life of 5,370 years. In other words it takes that long for half of it to be gone.
Measuring how much Carbon-14 remains in a sample gives an accurate indication of how old it is.
How did it get there in the first place?
Cosmic rays are constantly bombarding our atmosphere.
When they interact with nitrogen, carbon-14 is created. It combines with oxygen to create a radioactive variant of carbon dioxide.
Plants then take in this radiocarbon. Animals, ourselves included, eat the plants and absorb it. When the plants, animals or we die that process stops.
But the carbon-14 goes on decaying, so a sample of organic matter like wood or bone will give an indication of when the plant or animal died.
Researchers are constantly refining the "calibration curve" of carbon-14 levels to give an more accurate indication of the age of a sample.
Techniques have been developed so that ever smaller samples can be dated.