A<unk>  is a precursor cell to a promegakaryocyte, which in turn becomes a megakaryocyte. It is the beginning of the thrombocytic series.
It derives from an CFU-Me colony unit of pluripotential hemopoietic stem cells.
Megakaryoblast
Megakaryocyte
Lymphoblast
Histiocyte
Proerythroblast
Immunoblast
Ameloblast
Monocyte