CLOCK and teratoma: Using human tissue samples, we demonstrate a) that DNAm age strongly correlates with chronological age in the endometrium, b) that ectopic tissue is substantially younger than eutopic tissue according to the epigenetic clock, c) that tissue migration through metastasis does not change DNAm age, and d) that ectopic endometriotic lesions and teratomas share age deceleration that is not as young as pluripotent embryonic or induced pluripotent cells according to the epigenetic clock.