degradation of the sample. Then, handling of the materials is usually done in a physically isolated work area and under specific conditions (i.e. specific Temperature, moisture, etc...) also to avoid contamination and further loss of sample. Once the material has been obtained, depending on what it is, there are different ways to isolate and purify it. DNA extraction from fossils is one of the more popular practices and there are different steps that can be taken to get the desired sample. DNA extracted from amber-entombed fossils can be taken from small samples and mixed with different substances, centrifuged, incubated, and centrifuged again. On the other hand, DNA extraction from insects can be done by grinding the sample, mixing it with buffer, and undergoing purification through glass fiber columns. In the end, regardless of how the sample was isolated for these fossils, the DNA isolated must be able to undergo amplification. Amplification The field of molecular paleontology benefited greatly from the invention of the polymerase chain reaction(PCR), which allows one to make billions of copies of a DNA fragment from just a single preserved copy of the DNA. One of the biggest challenges up until this point was the extreme scarcity of recovered DNA because of degradation of the DNA over time. Sequencing DNA sequencing is done to determine the order of nucleotides and genes. There are many different materials from which DNA can be extracted. In animals, the mitochondrial chromosome can be used for molecular study. Chloroplasts can be studied in plants as a primary source of sequence data. In the end, the sequences generated are used to build evolutionary trees. Methods to match data sets include: maximum probability, minimum evolution (also known as neighbor-joining) which searches for the tree with shortest overall length, and the maximum parsimony method which finds the tree requiring the fewest character-state changes. The groups of species defined within a tree can also be later evaluated by statistical tests, such as the bootstrap method, to see if they are indeed significant. Limitations and challenges Ideal environmental conditions for preserving DNA where the organism was desiccated and uncovered are difficult to come by, as well as maintaining their condition until analysis. Nuclear DNA normally degrades rapidly after death by endogenous hydrolytic processes, by UV radiation, and other environmental stressors. Also, interactions with the organic breakdown products of surrounding soil have been found to help preserve biomolecular