Abstract: The present invention relates to field of fertility. The invention identifies biological ovarian markers from follicular cells, from follicular fluid, from cumulus cells and from oocytes which are indicative of follicular maturity in mammals. Described are methods for improving ovarian stimulation, methods for assessing maturity of a mammalian ovarian follicle, methods for optimizing in vitro maturation (IVM) and methods for classifying an embryo, these methods being based on assessment of expression level of ovarian markers indicative of maturity. Also described are methods for screening compounds stimulatory of or inhibitory to mammalian follicular maturation, kits for evaluating follicular maturity.