False-colour scanning electron micrograph (SEM) of a group of human chromosomes, thread-like structures in the cell nucleus that carry genetic information in the form of genes. Each chromosome is seen to consist of two strands (chromatids) joined in a region known as the centromere or kinetochore. Each chromosome is capable of constructing an exact copy of itself whilst the cell is in its resting stage between successive cell divisions. When chromosome division occurs, the centromere splits longitudinally. The nucleus of every human cell contains 46 chromosomes, 23 of maternal & 23 of paternal origin.