Colposcopy was first introduced in 1925 in Germany by Hans Hinselman. A colposcopeworks on the hypothesis that by magnifying the cervix and applying good illumination, early stages of cervical cancer could be picked -up. Other workers in the field include Schiller, Papanicolou, and Ayres who all contributed to the early detection of cervical cancer. The basic issue is the transformation zone (TZ). It is an area that forms from squamous metaplasia of columnar epithelium. The area where the two epithelia meet is referred to as the squamo-columnar junction SCJ. It is the most important landmark in cytology and colposcopy, where 90% of cervical neoplasm originates. More units are incorporating colposcopy into their practice so as to improve care of women with abnormal smears. Therefore, understanding of the scientific basis of colposcopy is important in carrying out the procedure according to agreed international standards.