Primordial Follicle
(Primary oocyte with 1 layer of follicular cells)
Primary Follicle
(Oocyte enlarged, follicular cells cuboidal and now called 'granulosa cells', zona granulosa present)
Secondary Follicle
(Follicular antrum appears in the zona granulosa, theca interna & externa develops)
Graafian Follicle
(Antrum greatly enlarged, secondary oocyte surrounded by corona radiata)