摘要Hematopoietic stem cell(HSC)transplantation is the only curative therapy for many dis-eases.HSCs from umbilical cord blood(UCB)source have many advantages over from bone marrow.However,limited HSC dose in a single CB unit restrict its widespread use.Over the past two decades,ex vivo HSC expansion with small molecules has been an effective approach for obtaining adequate HSCs.Till now,several small-molecule compounds have entered the phase Ⅰ/Ⅱ trials,showing safe and favorable pharmacological profiles.As HSC expansion has become a hot topic over recent years,many newly identified small molecules along with novel biological mechanisms for HSC expansion would help solve this challenging issue.Here,we will give an overview of HSC biology,discovery and medicinal chemistry development of small molecules,natural products targeting for HSC expansion,and their recent clinical progresses,as well as potential protein targets for HSC expansion.