<p>An essential requirement of human/medical cytogenetics is the unequivocal identification of each chromosome and its nomenclature. A karyotype is the standard arrangement of the diploid chromosomes of a species. In the Denver Conference in 1956, a standard human karyotype was agreed upon, which classified human chromosomes in 7 groups (A–G) of metacentric, submetacentric, subtelocentric, and acrocentric chromosomes. However, it was soon realized that there was some overlapping of chromosome size and morphology to distinguish one chromosome pair from another, especially in the B, C, and D groups of chromosomes. Development of chromosome banding techniques (e.g., G-banding), which differentially stained chromosomes through their length, made it possible to identify each chromosome from all others. Differential staining of the bands led to the development of an International System of Human Cytogenetic Nomenclature (ISCN), which enabled the identification of even small structural changes in the chromosomes. Now that more efficient, electronically based, newer, and more rapid techniques of preparing karyotypes are available, their utility in medical cytogenetics is going to enhance even further.</p>