Endometriosis is a disease affeting one tenth of all young women, causing chronic lower abdominal pain and problems in getting pregnant. Our research is focusing on the pathogenesis of the disease. Endometrial stem cells are like the mother cells that could replace any dying cells. It had been studied, but it is the first time to take transmission electron microscopic photos of what we suspect to be stem cells. Being active cells, one can see all the organelles for manfacturing new cells.