Day 7 to 20 hEB cells contain clonogenic, multilineage erythromyeloid progenitors for both primitive and definitive hematopoiesis. (A) Kinetics of mixed, multipotent erythromyeloid primitive (Mixed CFC-P) or definitive (Mixed CFC-D) colonies. (B) Kinetics of primitive macrophage (Macro-P) colonies and definitive GM-CFC and M-CFC (scored in combination and presented together as “GMCFC-D”). Shown is a representative experiment performed 3 independent times. Large, loosely packed primitive mixed erythromyeloid colonies (C; MIXED-P, magnification × 100) containing foamy macrophages and primitive erythroblasts (C; Wright stain, MIXED CFC-P, magnification × 600, oil) peak from day 9 to 12 hEBs (along with primitive erythroid CFCs) and differentiate from blast colonies similar to those that arise from MHE clusters. (D) Foamy macrophage colonies with no evidence of monocytic precursors on Wright stains (magnification × 1000, oil) also predominated from day 9 to 15 hEBs. (E) Compact colonies containing definitive monocytes/granulocytes (MIXED CFC-D) as well as GMCFC-D (F, left and middle; magnification × 1000, oil) and M-CFC-D (F, right; Wright stain, magnification × 600, oil) arose primarily from day 12 to 20 hEBs. (G) Day 9 hEB-derived MIXED CFCs (C) were picked (2 to 3 colonies) and shown by FACS analysis to express abundant amounts of CD71 and CD45 (as well as CD13; not shown). Shown in the bottom row is the FACS profile of day 9 hEB pooled EryP colonies from the same cultures.