Development of the renal ureteric bud/collecting duct system. The ureteric bud begins as an unbranched epithelial tube that invades the metanephrogenic mesenchyme, and recruits cells of that mesenchyme to form a `cap' (this cap becomes the stem cell population that produces nephrons). The ureteric bud then bifurcates, and the cap splits along with it. As the branches of the ureteric bud grow, pieces of distal cap left behind differentiate to make first a nephrogenic condensate and then to become an epithelial early nephron. This process repeats to form a ureteric bud tree (the future collecting duct) and the nephrons that will later connect to it. A much more detailed, illustrated account of renal development can be found at www.gudmap.org.