Overview of some factors implicated in follicle recruitment for maturation. (A) Summary and representation of principal macroscopic changes between primordial and primary follicles. (B) Representation of the principal factors implied to be involved in primordial follicle activation, and their relations, when they are known. Ooocyte-transcribed factors are in black, granulosa-transcribed factors are in red and factors originating from other follicles or of unknown origin are in grey. Activation is represented by an arrow and repression by a blunt arrow.