Final answer:
Primordial follicles are the earliest follicle type in the ovary, consisting of a primary oocyte surrounded by a single layer of granulosa cells.
Step-by-step explanation:
Primordial follicles are the earliest type of follicles in the ovary. They consist of a primary oocyte surrounded by a single layer of granulosa cells. This follicle type is the least developed and remains in a resting state until it is recruited for further development. They can stay in this resting state for years before they start to grow and mature.