Scientists are capable of retrieving genetic information from hair, skin, blood, sperm, tissue, and saliva as long as the sample contains intact DNA. Nucleotide sequences between humans differ by only 0.1%. Even so, this 0.1% includes approximately three million bases.  DNA can be analyzed through restriction fragment length polymorphism (RFLP) and Polymerase chain reactions (PCR). The RFLP process was introduced in 1988. Restriction enzymes digest portions of the DNA, leaving short fragments. These fragments are sorted through gel electrophoresis. The gel demonstrates the length of the fragments allowing specialists to determine whether the fragments came from the same person. PCR is more commonly used today because it more efficient and requires smaller samples of genetic samples.