[1][2] In 1910, after obtaining his Ph.D from the University of Munich, Papanikolaou then returned to Athens, where he married Andromachi Mavrogeni, who later became his laboratory assistant and research subject.

[7] Papanikolaou was also inspired by the philosophy of Immanuel Kant and Friedrich Nietzsche, Arthur Schopenhauer and Johann Wolfgang von Goethe,[8][9] writing papers on philosophical matters for an Athenian literary quarterly.

The book discusses the preparation of vaginal and cervical smears, physiologic cytologic changes during the menstrual cycle, the effects of various pathological conditions, and the changes seen in the presence of cancer of the cervix and of the endometrium of the uterus.

[15] His wife Andromachi Papanikolaou, known as Mary, continued his work at the Papanicolaou Cancer Research Institute after his death; she died in Miami on 13 October 1982.

[18] In 1920, Georgios Papanikolaou realized that he could tell the difference between normal and malignant cells on the cervix by viewing smears on a slide under a microscope.

[16] In 1925, with funds from the National Research Council and the Maternal Health Committee, Papanikolaou recruited 12 hospital staff volunteers, together with a number of pregnant gynecological and surgical patients, for a systematic study of cervical cell morphology.

[19] Upon examination of a slide made from a smear of one of the participant's vaginal fluid, Papanikolaou discovered that abnormal cancer cells could be plainly observed under a microscope.

"The first observation of cancer cells in the smear of the uterine cervix," he later wrote, "gave me one of the greatest thrills I ever experienced during my scientific career.

"[19] In 1928, Papanikolaou told an incredulous audience of physicians about the noninvasive technique of gathering cellular debris from the lining of the vaginal tract and smearing it on a glass slide for microscopic examination as a way to identify cervical cancer.

At a 1928 medical conference in Battle Creek, Michigan, Papanikolaou introduced his low-cost, easily performed screening test for early detection of cancerous and precancerous cells.

Papanicolaou's next communication on the subject did not appear until 1941 when, with gynecologist Herbert Traut, he published a paper on the diagnostic value of vaginal smears in carcinoma of the uterus.

His method of cancer diagnosis was published in a French medical journal, La Presse Médicale, on 11 April 1928,[24] but Papanicolaou was not aware of Babeș's research.

[16] Babeș's technique of preparing, staining and examining vaginal smears was substantially different from Papanicolaou's and would never have lent itself to mass screening for cervical cancer without modification.

[28] Recent scientific papers have analyzed the ways that Babeș's method differed from Papanikolaou's and note that the paternity of the Pap test belongs solely to Papanicolaou.