In a recent paper in the New England Journal of Medicine, researchers at Brigham and Women's Hospital in Boston report their discovery of stem cells in the human lung, reports the Associated Press' Malcolm Ritter. The researchers believe that the cells can make a wide variety of lung tissues and could eventually be used to treat emphysema and other diseases. When the cells were injected into mice, they rebuilt airways, air sacs, and blood vessels within two weeks, Ritter says. Experts say the finding is a giant step forward in a difficult field of study, if the findings bear out in humans as they did in mice, he adds. The study's authors say that it's too early to tell which diseases might be one day be treatable with the cells, but that they are initially looking at emphysema and pulmonary hypertension as possibilities. These cells may also be useful in building up lung tissue after surgery, Ritter says, although he adds that it's unclear whether they could be used to treat asthma as yet.