Hideo Ema is a professor at Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College. He previously worked with Drs. Toshio Suda, Hiro Nakauchi, Neal Young, Ihor Lemischka, Ana Cumano and many others. He has long been interested in HSC biology, particularly how to induce in vitro self-renewal in HSCs. He greatly contributed to the establishment of single-cell transplantation, single-cell culture, single-cell immunostaining, paired daughter cell experiments, and single-cell PCR. Using these techniques, he will take a unique approach to ex vivo expansion of HSCs. In vitro colony assay is a well-established technique originally developed by Drs. Metcalf and Sachs. Dr. Ogawa used this assay to characterize many cytokines. The importance of this assay in HSC study has almost been forgotten in recent years. He attempts to be a successor to these legendary people, showing its usefulness in a modern way.