With the combination of bisulfite conversion and high-throughput sequencing techniques, it is now possible to generate genome-wide single base resolution maps of cytosine methylation, referred to as whole-genome bisulfite sequencing (WGBS). This has revolutionized the way scientists study epigenetics. Epigenetics is the study of heritable changes in gene expression that occur independently from changes in nucleotide sequence. Before WGBS, methylation could only be determined in small regions at a time or at low resolution, but now it is possible to track single methylation polymorphisms across generations.