Chromosomes are thread-like structures made of DNA and proteins, found in the nucleus of eukaryotic cells. Each chromosome consists of two identical halves called sister chromatids, joined at a region known as the centromere. The DNA in chromosomes carries genetic information essential for the development and functioning of an organism. The structure of chromosomes is organized into distinct regions, including the telomeres at each end, which protect the chromosome from deterioration. During cell division, chromosomes condense and become visible under a microscope, allowing scientists to study their number and structure, which is crucial for understanding genetic disorders and heredity.