Historically in clinical cytogenetics, G-banding has been the gold standard for detecting gross chromosomal abnormalities, ranging from simple numerical changes to the identification of complex structural rearrangements in clinical samples. The designation “marker chromosome” or “derivative chromosome” has been used to indicate that G-banding has been unable to provide a definitive identification of the aberration. This is often because the complexity of the rearrangement has resulted in the lack of a coherent and recognizable banding pattern. The advent of the various multicolor fluorescence in situ hybridization (FISH) chromosomal painting techniques (1 ,1 ) has greatly improved our ability to identify all marker chromosomes, but these techniques still need some careful planning in rapidly achieving the goal of identifying complex chromosomal rearrangements.