A flake of skin...a strand of hair...a fleck of saliva...a drop of blood...everywhere we go we leave behind bits of ourselves that are as unique as fingerprints. Each cell contains genetic material called DNA, which holds information that scientists can use to learn about the person who left those cells behind. In the past twenty-five years, researchers have made significant advances in all disciplines of science, including the study of genetics. As science has leapt forward, the effect on forensics has been remarkable. New knowledge of DNA has dramatically changed the amount of information available to forensic scientists at the scene of a crime, opening doors that were never open before.