Final answer:
Primordial follicles consist of a single oocyte surrounded by a single layer of flat granulosa cells, representing the earliest stage in the development of ovarian follicles.
Step-by-step explanation:
The primordial follicle consists of a single oocyte and a single layer of flat, also known as squamous, granulosa cells. These follicles are the least developed of the ovarian follicles and represent the earliest stage of folliculogenesis, which is the process of follicle development in the ovaries. During folliculogenesis, after puberty, a few primordial follicles respond each day to recruitment signals and transition into primary follicles with active granulosa cells that change from a flat to a cuboidal shape as they divide and proliferate.