Fluorescent In situ Hybridization, is fast and specific technique which can be used to detect alteration in numerical and structural chromosomal anomalies. With technological advancement multicolour FISH (m-FISH or SKY FISH) can be carried out and single probe (for just one chromosome) can also be carried out as per the need of case. It can also be employed in small deletion, duplication, translocation and chromatin fusion attributed disorders. Certain key features that make FISH a valuable tool is turn around time, which is less than 24 hours. Another advantage of FISH based analysis is it can be carried out in interphase nuclei, ruling out the need of culture and thus playing a crucial role in non dividing cells or dead cells where chromosomal analysis is not possible. Few of FISH based test are enlisted below and situations where those tests can be utilized.