Technical Abstract: Gametogenesis is the process of gamete formation, which includes microgametogenesis and megagametogenesis. Gametogenesis initiates after specialized cells in the sporophyte undergo meiosis, and subsequent mitotic divisions yield the gametophyte phase of the plant life cycle. In higher plants, microgametogenesis occurs in the anther, producing tricellular pollen with two sperm cells within a vegetative cell. Megagametogenesis occurs in the ovule, producing an embryo sac. The male gametes, the two sperm cells, and the female gametes, the egg and central cell, fuse to yield the zygote and the endosperm, respectively. Both micro-gametogenesis and megagametogenesis are under strict genetic control. Studies of gametophyte mutants have identified genes important for gametogenesis. Furthermore, high-throughput expression profiling techniques have helped identify gene regulatory networks that operate during gametogenesis.