Results . Clustering of cells during postnatal kidney development of rats . In the present study, six-time points were chosen for mapping the gene expression of postnatal kidney development in rats: postnatal days 0, 2, 5, 10, 20, and 56, which correspond to kidney development stages in most human preterm infants according to pathological findings. During postnatal day 0–postnatal day 5, nephrogenesis was clearly detected. At this age, the comma- and S-shaped bodies were detected in the out...