This book describes the most important techniques used for studying cfDNA in the different samples; serum, plasma, urine. Chapters detail methods on liquid biopsy for cancer disease, methods in cancer, epigenetic modifications, fetal and pediatric diseases, physical activity, and urinary cell free DNA. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls.