Now, researchers have brought these together in ‘assembloids’ which are the most mature and complex kidney structures grown in the lab to date. Lab grown human kidney assembloid showing the formation of radial nephrons connected to a central collecting system. They filtered blood, took up proteins such as albumin, secreted kidney hormones and exhibited the early signs of urine production. A lack of newborn human kidney samples meant they could not determine the exact level of development for the human assembloids, though they did mature at least beyond the embryonic stage. “Our study provides a powerful new tool for studying a wide range of complex kidney diseases, as well as strong foundation for engineering functional synthetic kidneys as a lifesaving option for the patients who need them,” says Li.