Lab-grown miniature kidneys have shocked scientists by developing brain and brawn. A study said that the mini organs, known as organoids growing from stem cells, surprisingly developed brain and muscle cells, Live Science website said. Scientists studied thousands of kidney organoid genes in 83,000 cells drawn from 65 mini kidneys. They found that 20 per cent of the cells had gone rogue, developing into cells of other tissues, according to study co-author Benjamin Humphreys of Washington University School of Medicine in St. Louis. Scientists grow mini organs by placing stem cells in a concoction of nutrients that prompt their development into the desired organoid.