Although this technique can provide robust semi-quantitative assessment of the modified forms of cytosine bases where detectable, it cannot be used for evaluating the absolute levels of 5mC or its oxidation derivatives. Therefore, we recommend the use of other complementary but quantitative approaches16, 19 -24. Since the discovery of 5mC oxidation derivatives in mammalian genomes, several approaches have been developed to study their biological roles16, 19-24. Although these approaches can be valuable in determining the absolute levels of 5mC oxidation derivatives, they do not provide information concerning their spatial distribution20, 26. We have successfully used the method described here to map the spatial distribution and localization of 5mC oxidation derivatives in different cell types of the developing and adult brain20