Ovarian cancer represents a highly heterogeneous group of tumors with distinct histomorphology and clinical outcome. The cells of origins for ovarian cancers have been highly controversial, from ovarian epithelial cells, fallopian tubal epithelial cells, and ovarian or fallopian tubal stromal cells. Pathologically, the ovarian cancer can be divided into two major groups, the tumors resembling to the cells of the origin such as endometroid, mucinous, serous borderline/low-grade serous carcinoma, while second group of tumors that display the morphology that is dissimilar to the cell or tissue of origin, such as high-grade serous carcinoma, clear cell carcinoma, or malignant mixed mullerian tumors. A unified “life code” model is presented to explain the tumors with two distinct morphologic phenotypes: The first group of tumors is likely to be from the tissue differentiation blockage or maturation arrest, while the second group of tumors is likely to be from de novo malignant transformation from the formation of polyploid giant cancer cells with blastomere-like properties. The different views of cells of origins and other models of tumorigenesis will be also presented together with this new model so to reflect the evolving concept change of ovarian epithelial tumorigenesis that has puzzled the pathologists for centuries.