The kidney develops from special cells called nephron progenitor cells (NPCs), which create the nephrons—the structures that filter blood. Scientists can make NPC-like cells from human stem cells, but these cells normally exist only briefly and don’t fully resemble the real cells found in the body. In this work, researchers developed a new method to grow these NPC-like cells in large numbers and keep them stable over time. With an improved culture medium, the lab-grown cells become much more similar to true human NPCs and continue dividing while maintaining their identity. Using this method, the team can also produce kidney organoids—tiny kidney-like tissues—with fewer incorrect cell types and more mature filtering structures. This streamlined process takes about two months and offers a more reliable way to study kidney development and disease.