The author and Dr Susumo Ohno (left), whose original observations of the morphology of the mammalian X-chromosome provided the author with the idea that only one of the 2 X-chromosomes was active, the other undergoing inactivation in early embryogenesis. This photograph was taken in my laboratory at the City of Hope Medical Center and published in Time Magazine, January 4, 1963, to accompany a feature article entitled, “Research Makes It Official: Women Are Genetic Mosaics.” The insert shows the hyperchromatic X-chromosome of a female. The photographer paid no heed to the author's insistence that the burette with which we are posed had nothing to do with X-inactivation.