How do metabolic pathways operate in stem cells? We have shown that in the hematopoietic system cell differentiation is accompanied by metabolic differentiation. Each hematopoietic cell type has a distinct metabolic signature. Almost all metabolites show cell type-specific enrichment patterns, mostly for unknown reasons. We are interested in understanding why different cell types have different kinds of metabolism and in uncovering novel roles for metabolites in hematopoietic stem cells and other hematopoietic cell types.