In the late 1960s Caspersson developed banding techniques which differentially stain chromosomes. This allows chromosomes of otherwise equal size to be differentiated as well as to elucidate the breakpoints and constituent chromosomes involved in chromosome translocations. Deletions within one chromosome could also now be more specifically named and understood. Diagrams identifying the chromosomes based on the banding patterns are known as cytogenetic maps. In the 1980s advances were made in molecular cytogenetics. While radioisotope-labeled probes had been hybridized with DNA since 1969, movement was now made in using fluorescently labeled probes. Hybridizing them to chromosomes preparations made using existing techniques came to be known as fluorescent in situ hybridization (FISH). This change significantly increased the usage of probing techniques as fluorescently labeled probes are safer and can be used almost indefinitely (Wikipedia, oct. 2008).