In situ hybridization (ISH) is a method used to detect specific nucleic acid sequences in tissues or cells. By hybridizing labeled nucleic acid probes to target DNA or RNA in a sample, ISH can locate the location of specific genes or RNA molecules at the cellular or tissue level. This technology is widely used in the study of gene expression, gene localization and cell differentiation. There are multiple variants of ISH, including in situ PCR, in situ RT-PCR, etc., which provide a powerful tool for in-depth understanding of biological processes.