This issue of Seminars in Dermatology describes our current understanding of the molecular nature of skin diseases. Some would say it is hubris to even contemplate this charge considering the rapid progress in molecular genetics. We implore the gods protecting the nucleotides to look kindly on our efforts. This introductory article discussed some general methodological considerations and techniques and provides a glossary of common terms used in molecular biology, useful for understanding this issue of Seminars in Dermatology. This article is aimed at neophytes to enhance their ability to enter the magical realm of the gene. The articles in this issue describe diseases with a defined defect at the DNA level or diseases in which there is a rapid closing in on the basic defect.