This revised and updated edition of a recognized classic emphasizes tissue and cell in situ hybridization methods. Among the new techniques detailed are PNA probes for viral diagnostics, plant in situ hybridization, cell proliferation detection, and quantitation of in situ hybridization. There are also cutting-edge techniques for tissue microarrays, expanded embryology-developmental gene detection, and expanded cell culture. Derivative techniques presented include identification of transplanted cells, histones, nick-end labeling for apoptosis, the use of peptide nucleic acid probes, and in situ hybridization of plant specimens. The protocols follow the successful Methods in Molecular Biology(t) series format, each offering step-by-step laboratory instructions, an introduction outlining the principles behind the technique, lists of the necessary equipment and reagents, and tips on troubleshooting and avoiding known pitfalls.