Cytogenetics is a branch of genetics which studies the structure and function of the cell, especially the chromosomes and the related disease states caused by abnormal chromosome number and/or structure. Some of the widely used molecular cytogenetic techniques are Fluorescence in situ Hybridization (FISH), Comparative Genomic Hybridization (CGH), Spectral Karyotyping (SKY), Optical mapping etc. Fluorescent in-situ hybridization is one of the most commonly used molecular cytogenetic techniques has become an important complementary application in genetic studies. The use of variable FISH techniques enhanced the thorough interpretation of numerical and complex chromosomal alterations, bridging the gap between the conventional chromosome banding analysis and molecular DNA studies.