The ovarian reserve represents the fertility potential for every woman and is defined as the population of quiescent follicles within the ovary. Initiation of the resting follicle pool commences in the fetus, then experiences a progressive decline in follicle numbers from birth onwards, yielding around 450 mature and fertilizable oocytes in the course of the reproductive lifespan. Numerous factors can damage the ovarian reserve, including oncological treatments, surgery, inflammatory conditions, immune disorders, and even advancing age, seriously compromising fertility. Developing effective strategies to protect the follicle pool is challenging for several reasons, including lack of knowledge about all the players involved in follicle quiescence maintenance, recruitment, and growth, inadequate understanding of the mechanisms responsible for preserving full oocyte potential, upon which embryo development depends. This Methods Collection aims to encourage further research into the biological mechanisms regulating ovarian reserve maintenance and safeguarding fertility potential. More specifically, authors are invited to contribute (i) methods of developing ex vivo, in vitro, and in vivo models to investigate follicle pool and oocyte maturation, and (ii) protocols for follicle and oocyte analyses using imaging and molecular biology techniques. These joint efforts of sharing novel techniques and standardizing existing approaches lead to significant advances in devising strategies for infertility treatments and fertility restoration after gonadotoxic injury.