design: 1. Take genome DNA samples for quality control;2. Fragmented genome DNA to the mean size of 200-350bp;3. Blunt-ending and 3'-end dAaddition;4. Methlated adaptor ligation;5. Bisulfite conversion with EZ DNA Methylation-Gold kit (ZYMO);6. PCR amplification;7. Library quality control;8. Library circularization;9. The library was amplified to make DNA nanoball (DNB);