In addition to turning into different kids of tissues, in mice, at least, it seems stem cells can exude "healing factors" that repair the lungs of newborn preemies.
They simulated premature birth by giving the newborns oxygen, which damages the lungs. Then they injected stem cells into the airways of half the mice. In two weeks, the treated mice could run twice as far as the untreated. Necropsy showed the stem cells had not just prevented further damage but had repaired the existing damage.
It has occurred to the researchers that they should look into what is in the liquid that the stem cells produce, because there might be further uses for it, or things like it.