['Existing dogma that a female is born with fixed number of eggs was challenged by the detection of stem cells in adult mammalian ovary. Data has accumulated in support of ovarian stem cells (OSCs) proliferation, maintenance in culture, formation of germ cell nests and differentiation into oocytes and primordial follicle assembly using different strategies.', 'Flow cytometry analysis identified >8\xa0μm OSCs which are DDX1 positive and are considered equivalent to spermatogonial stem cells (SSCs) in testis. Analysis of both ovarian and testicular smears obtained after enzymatic digestion has led to the identification of an additional stem cell population termed very small embryonic-like stem cells (VSELs). VSELs and OSCs/SSCs differ from each other in their size and OCT-4 expression. VSELs express pluripotent markers including nuclear OCT-4 whereas OSCs/SSCs express cytoplasmic OCT-4 suggesting a differentiated state. VSELs can be studied by flow cytometry as small sized cells which are LIN-/CD45-/Sca-1+. We have reported 0.02\u2009±\u20090.008, 0.03\u2009±\u20090.017 and 0.08\u2009±\u20090.03\xa0% of total cells as VSELs in normal, chemoablated and after FSH treatment to chemoablated mouse ovary.'] Are ovarian stem cells always accompanied by very small embryonic-like stem cells in adult mammalian ovary?