Somuchofwhatweknowaboutthepathogenesisofhumandiseasehascomefromthe systematic and careful study of histological material. Indeed, every internal medicine discipline has its landmark papers describing the clinico-pathological correlations. However, increasingly, it is molecular and cellular biology that provides the necessary mechanistic insights. For many years, it was thought that the two skill sets were mutually exclusive, but we hope that this book shows that this is not necessarily so. Implicitinthescienceofhistologyisthepreservationandarchivingoftissue. PartIof the book concentrates on the preparation of tissue, providing an overview of fixation, embedding, and processing (Chapter 1), and in Chapters 2 and 3, the required techniques for the retrieval of RNA from histological sections. Both routine and specialist histological staining techniques