Chromosomes are long, thread-like structures made of DNA and proteins that carry genetic information. They are found in the nucleus of cells and play a crucial role in heredity, as they contain the genes that determine an organism's traits. Humans typically have 46 chromosomes, arranged in 23 pairs, with one set inherited from each parent. During cell division, chromosomes become tightly packed to ensure that DNA is accurately copied and distributed to daughter cells. Each chromosome consists of two sister chromatids joined at a region called the centromere. Proper chromosome function is essential for growth, development, and reproduction in all living organisms, including humans.