The application of the field of organic chemistry called stable isotope analysis that has been used to identify evidence for human diet and place of origin from human tooth and bone. Oxygen isotope analysis, for example, studies the slightly different chemical make ups of oxygen atoms, known as isotopes. Water from different parts of the world contain different proportions of these isotopes, which are absorbed into our adult teeth before they become covered in enamel, when we drink water. This means that it is possible to determine where in the world someone was drinking water (and therefore probably living) around the age of 7 years old.