Anthers are the male reproductive structures of flowering plants that produce pollen. Each anther is deeply bi-lobed and each lobe contains two structures called microsporangia. At the center of each microsporangium are numerous mother pollen cells that, after undergoing meiosis, form microspores or pollen grains. Nutrients are provided to a developing cell by columnar shaped tapetum cells that surround each microsporangium. During the late prophase stage, the tapetum cells are usually microscopically visible. Upon maturing, the pollen grains are released by the anther and made available for transport to a female reproductive organ called the stigma.