How are reticulocytes?

They are RBC nucleated, they carry alot of RNA and can be detected by supravital staining live 2-3 days, 2% of RBCs, number of reticulocytes is useful in clinical test (increased ->marrow more active than normal, decreased ->production problem) They come from pronormoblast, which gives normoblasts, that differentiate into reticulocyte which loses its nucleus to become RBC