Abstract: In humans, early oogenesis determines by birth the number and quality of eggs for the entire lifespan, but a complete understanding of this fascinating and dynamic process is lacking. I will present our research efforts in zebrafish and their contributions to understanding the cell and developmental biology of early oogenesis. I will focus on two recent studies: 1) a newly identified cilium we discovered in the early oocyte, which is essential for meiosis and germ cell morphogenesis, and 2) a conserved membraneless organelle in oocytes called the Balbiani body, and our findings on deciphering its mechanisms of formation.