Fluorescence in situ hybridization (FISH), is an example of a genetic labeling technique that utilizes probes that are specific for chromosomal sites along the length of a chromosome, also known as chromosome painting.  Multiple fluorescent dyes that each have a distinct excitation and emission wavelength are bound to a probe which is then hybridized to chromosomes.  A fluorescence microscope can detect the dyes present and send it to a computer that can reveal the karyotype of a cell.  This technique allows abnormalities such as deletions and duplications to be revealed.