All flowering plants show sexual reproduction. Flower is the unit of sexual reproduction . Thalamus bears four floral whorls that are calyx , corolla , androecium and gynoecium , among these calyx and corolla are non essential whorls , androecium and gynoecium are essential whorls. Androecium composed of stamens. Stamen is male reproductive structure ,it is also called as microsporophyll. Upper swollen fertile part of the stamen is anther .Most common type of anther is dithecus and tetrasporangiate . In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus. When the anther is young, a group of compactly arranged homogenous cells called the sporogenous tissue occupies the centre of each microsporangium. As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads. The process of formation of microspores from a pollen mother cell (PMC)through meiosis is called microsporogenesis. The microspores, as they are formed, are arranged in a cluster of four cells–the microspore tetrad. Four cells of microspore tetrad are associated with the help of a chemical substance that is callose ,gradually callose gets dissolves and  the microspores dissociate from each other and develop into pollen grains.