cDNA libraries are being created from zebrafish embryonic cells expressing LMO-2 promoter driving green fluorescent protein in early development and from mouse hemangioblasts expressing Scl (truncated inactive human CD4 knock in) and Flk in an in vitro ES cell differentiation assay. Gene expression profiles from these two cell populations will be analyzed by direct sequencing of normalized cDNA clones. This comparative gene expression analyses will improve our understanding of stem cell biology at a molecular level.