We know that circulating tumor cells (CTCs) are cancer cells that "fall" into the peripheral blood. These cells spread with the blood to form new metastases in other parts of the body, so they are closely related to the metastasis and recurrence of cancer. However, circulating tumor cells are very rare in peripheral blood, which brings great difficulty to the development of related research. About 1 circulating tumor cell for every 1 billion blood cells! A new type of circulating tumor cell detection method developed by scientists at the University of Michigan in the United States goes beyond current technology to study each circulating tumor cell with ultra-high purity for the first time.