Multicolor fluorescence in situ hybridization (mFISH) assays are essential for a precise description of chromosomal rearrangements. Routine application of such techniques on human chromosomes started in 1996 with the simultaneous use of all 24 human whole chromosome painting probes in multiplex-FISH (M-FISH) and spectral karyotyping (SKY), even though the principle of mFISH was reported in 1989. Numerous approaches for chromosomal differentiation based on mFISH assays have been established, predominantly, to characterize marker chromosomes, but also in evolutionary biology, nuclear architecture, zoology and botany. The mFISH Homepage, which reviews all available literature at http://www.med. uni-jena.de/fish/mFISH/mFISHlit.htm will be introduced here.
