[Top] Between 8.75 and 11.5 days, the Wolffian duct in the mouse embryo matures and acquires branching capacity. After 11.5 days, nephron and interstitial progenitor cells, as well as the ureteric bud, start to develop. Branching of the ureteric bud and higher-order kidney structures form at around 15.5 days. [Bottom] Previously developed PSC-derived kidney organoids contained randomly induced nephron structures which lacked organization and inter-nephron connections. Note the lack of branched ureteric epithelium and nephron progenitors.