This chapter discusses development, structure, and function of the follicle processes. It presents developmental, structural, chemical, and functional aspects of the microvilli and zona material for various fishes. The chapter also discusses the functional morphology of the follicular wall, egg surface components, and micropyle in the fish ovary by correlating the results of electron microscopic, histochemical, and biochemical studies carried out during the twentieth century. It reveals the great diversity in development, structure, and function in various fish species. The follicular epithelium synthesizes mainly proteins, as evidenced by the presence of numerous ribosomes, elements of granular endoplasmic reticulum, well-developed Zur funktion der Golgi complex, coated vesicles, and dense bodies. The chapter describes the possible mechanisms of transport of substances across their cellular membranes. The shape, structure, and origin of micropyles, which play an important role in fertilization of teleosts, show species variation. The surface pattern of eggs and the micropyles constitute important characteristic criteria for the identification of teleosts.