FISH, or Fluorescence In Situ Hybridization, is a laboratory technique used to detect and localize specific DNA sequences on chromosomes. This method involves using fluorescent probes that bind to the target DNA, allowing researchers to visualize the genetic material under a fluorescence microscope. FISH is commonly used in genetics, cancer research, and prenatal diagnosis. The technique is particularly valuable for identifying chromosomal abnormalities, such as deletions, duplications, or translocations. By providing precise information about the number and structure of chromosomes, FISH aids in understanding genetic disorders and can help guide treatment decisions in conditions like cancer and genetic syndromes.