An overview of human erythropoiesis. The early phase refers to the expansion of erythroid progenitors and is primarily sustained by interleukin-3 (IL-3) and stem cell factor (SCF). The late phase is dedicated to the maturation of erythroid precursors up to enucleation and is sustained by erythropoietin (EPO), although SCF continues to play a role in erythroid precursor expansion early in this phase. Throughout erythroid differentiation, the expression pattern of some surface markers changes and allows tracking by flow cytometry. Baso-E, basophilic erythroblast; BFU-E, burst-forming unit erythroid; CFU-E, colony-forming unit erythroid; HSPC, hematopoietic stem and progenitor cell; Ortho-E, orthochromatic erythroblast; Poly-E, polychromatophilic erythroblast; Pro-E, proerythroblast. Professional illustration by Somersault18:24.