Provided is a method of non-invasively diagnosing endometriosis in a subject comprising maintaining or culturing stromal cells, obtained from a menstrual effluent or discharge sample from the subject. Also provided is a method of non-invasively diagnosing fertility in a subject. Also provided is a kit for non-invasively diagnosing endometriosis in a subject. Also provided is a method of treating endometriosis in a subject. Also provided is a method of preventing the progression or development of endometriosis in a subject.