In situ hybridization technique utilizes the fact that DNA and RNA will undergo hydrogen bonding to complimentary sequences of DNA or RNA. By labeling sequences of DNA or RNA of sufficient length (approximately 50-300 base pairs), selective probes can be made to detect particular sequences of DNA or RNA. The application of these probes to tissue sections allows DNA or RNA to be localized within tissue regions and cell types. In situ hybridization is a powerful technique and unique in the way that it allows one to study the macroscopic distribution and cellular localization of DNA and RNA sequences in a heterogeneous cell population.