Is the pre-antral ovarian follicle the ‘holy grail’for female fertility preservation?

•The stock of pre-antral ovarian follicles represents an untapped potential, which could be ‘unlocked', for preservation or research purposes.•Advancements in in vitro culture and auto-transplantation of ovarian follicles will greatly improve fertility preservation strategies.•Pre-antral follicles provide a safe method for the restoration of fertility when in vitro follicle culture becomes a mainstream technique.•In the near future, it is expected that an artificial ovary and an in vitro culture system for primordial follicles will become available.