A centromere is a specialized region of a chromosome that plays a crucial role during cell division. It is the point where two sister chromatids are joined together, forming an X-shaped structure. The centromere ensures that each new cell receives an identical set of chromosomes when a cell divides, which is essential for maintaining genetic stability. During the process of mitosis or meiosis, the centromere serves as the attachment site for spindle fibers, which help pull the sister chromatids apart. This action ensures that each daughter cell inherits the correct number of chromosomes, contributing to proper cellular function and development.