Fluorescence in situ hybridization (FISH) is an emerging molecular cytogenetics technique, which is a non-radioactive in situ hybridization technique developed in the late 1980s based on the original radioactive in situ hybridization technique. It has been widely used in many fields such as genome structure study of plants and animals, chromosome fine structure variation analysis, virus infection analysis, human prenatal diagnosis, tumor genetics, and genome evolution study. The basic principle of FISH is to use a known labeled single-stranded nucleic acid as a probe to specifically bind to an unknown single-stranded nucleic acid in the material to be examined according to the principle of base complementarity to form a hybridized double-stranded nucleic acid that can be detected. Since DNA molecules are arranged linearly along the longitudinal axis of chromosomes, the probes can be hybridized directly into chromosomes to localize specific genes on the chromosomes.