In situ amplification techniques are designed to increase the mass of DNA in a fixed target, either whole cells or tissue sections. When combined with fluorescently labeled nucleotides, they can be used for locus detection. They also can be used to increase target mass for subsequent operations, such as cellular or chromosomal isolation by microdissection. When combined with chromosome microdissection, these techniques allow libraries to be made from single copies of chromosomes, chromosome fragments, or even bacteria.