This figure demonstrates a typical symmetric division of one CD34⁺/CD38⁻ cell derived from FLV. We found that the first cell division occurred consistently at 36 to 38 hours after culturing. Thereafter, the cell doubling time was 12 hours. Previous and subsequent experiments with shorter observation intervals (eg, every 3 hours) have demonstrated that cells might migrate, partly due to movements of the culture plates and partly due to the migratory property of the progenitor cells themselves.