Researchers have had success growing organs in controlled lab environments, but repeating that feat inside a complex, messy animal body? That's more than a little tricky. However, researchers at the University of Edinburgh have managed that daunting feat for the first time. They've grown thymus glands inside lab mice by "reprogramming" the genes in tissue-regenerating cells and partnering those with support cells. The team didn't have to use scaffolds or other "cheats" to trigger the growth; it just injected the cells and waited. There weren't even any obvious limitations. The organs were full size (unlike the baby-like results from some experiments), and they were just as efficient at producing virus-fighting T-cells as the real deal.