The global liquid biopsy industry is expected to exceed $US5 billion by 2023. One application of liquid biopsy technology is the diagnosis of disease using biomarkers found in blood, urine, stool, saliva, and other biological samples from patients. These biomarkers could be DNA, RNA, protein, or even a cell. More recently, the use of cell-free DNA from plasma is emerging as an important minimally invasive tool for clinical diagnosis. The development of technology has increased the diversity of its application. Here, we discuss how liquid biopsies have been used in the clinic, and how personalized medicine are likely to use liquid biopsies in the near future.