What is the earliest recognizable erythroid precursor using light microscopy?

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In erythropoiesis, the earliest erythroid precursor you can recognize on light microscopy is the rubriblast, also known as the pronormoblast. This cell sets the starting point for the erythroid series seen on Wright-Giemsa stained smears: it is large with a round, relatively open nucleus and finely dispersed chromatin, often with a visible nucleolus, and it has scant cytoplasm that stains deeply basophilic due to high RNA content and no hemoglobin yet. As maturation proceeds, the nucleus condenses and Hb starts to appear, so you see the next stages (basophilic erythroblast, then polychromatophilic erythroblast, and finally orthochromatic erythroblast) with progressively more eosinophilic cytoplasm and eventual nuclear extrusion. The basophilic erythroblast is a later step than rubriblast, and the orthochromatic erythroblast is still later, making rubriblast the earliest recognizable erythroid precursor on light microscopy.