Oogenesis is a unique process of cell division and differentiation, where a mature oocyte is formed from a germ cell precursor. In this chapter, the complex regulatory network responsible for oocyte differentiation and maturation in Drosophila melanogaster and human female gametogenesis is discussed. There is a focus in the hormonal and non-hormonal signaling pathways responsible for the communication between the oocyte and the surrounding somatic cells, with a special emphasis to starvation-dependent and age-dependent loss of female fertility.