FISH (Fluorescence in situ hybridization) is a cytogenetic technique developed by the researchers to detect the particular DNA sequence on chromosome. FISH uses fluorescently labelled probes that bind only to complementary sequences on the chromosomes. FISH technology determines the deletions which not visible by standard cytogenetic banding patterns; it helps to find out whether a particular genetic element is present or absent. It also helps to find deletion, amplification, and rearrangement of a gene, loci, or region. This unique capability of FISH technology provides strong reason for its diagnostic use in cancer, other genetic diseases.