During early stage of embryonic development, the liver bud, arising from the foregut endoderm,is the beginning for the formation of future liver three-dimensional structure.While the gene expression profiles associated with this developmental stage have been well explored, the detailed cellular events are not as clear.Epithelial-mesenchymal transition (EMT) was thought to be essential for cell migration in the early vertebrate embryo but seldom demonstrated in human liver development.In this study, we tried to identify the cell populations with both stem cell and EMT features in the human liver bud.Our in situ studies show that the phenotype of EMT occurs at initiation of human liver development, accompanied by up-regulation of EMT associated genes.