Double fertilization is a flowering plant mechanism whereby two immotile sperm cells fertilize two different female gametes. After double fertilization, a seed consists of the embryo, the endosperm and the seed coat, which develop from the zygote, the fertilized central cell and the maternal integuments, respectively. The embryo development in the early stage includes zygote formation, zygotic genome activation, the first asymmetric division and cell division, cell fate decisions until the epidermis, the vascular and other ground tissue appear. Meanwhile, the endosperm nuclei divide 7 to 8 times without cell division to form a syncytium, and then the cell wall separates the nuclei into individual cells. Also, the growth and elongation of seed coat cells coordinate with the reproductive tissue. In this part, we have a global view of interactions among the endosperm, the embryo and the seed coat to figure out the mechanism and signal pathway in this process. These research can help us increase the quality and crop yields in agriculture.