Formation of mature, fertile sperm involves dramatic changes in cell shape and formation of sperm-specific organelles needed for cell motility and fertilization. Spermatogenesis in the fruit fly Drosophila melanogaster is particularly dramatic, as developing sperm become nearly 2 mm long (~50x longer than human sperm) and form needle-shaped nuclei (~10x more condensed than in human sperm) during their differentiation. Drosophila sperm development begins by asymmetric division of a germline stem cell to give rise to a new stem cell and a daughter gonial cell, which divides mitotically and meiotically to produce a cyst of interconnected spermatids that differentiate to form mature sperm. We discovered that a class of membrane lipid signaling molecules, the phosphatidylinositol phosphates, or PIPs, is required for cell morphogenesis and organelle biogenesis at multiple stages of sperm development: PIPs are needed for cytokinesis during male meiosis, for cell polarization during spermatid elongation, for formation of functional sperm tails, and for nuclear shaping. Our ongoing studies will shed light on how PIPs and their regulatory enzymes control these conserved processes, which are important for male fertility.