In a span of 100 years between 1900 and 2000, three landmark discoveries almost equally spaced apart in time revolutionized the scope of the study of the molecular basis of life. These were: the rediscovery of Mendelism and the laws of heredity in 1900, the discovery of DNA structure in 1953, and the completion of the first draft sequence of the human genome in 2000 (published in 2001). Each of these discoveries represents a major breakthrough that paved the way for further progress in a new direction. With the elucidation of DNA structure in 1953 by James Watson and Francis Crick, and the subsequent deluge of discoveries on DNA replication, genetic code, mRNA synthesis, protein synthesis, and gene regulation, the findings of classical genetics could be explained in terms of molecular biology principles. Thus, the discovery of DNA structure paved the way for the merger of two apparently disparate disciplines—classical genetics and molecular biology, and the birth of molecular genetics.a,b Within another 50 years, the science of molecular biology/molecular genetics has u ndergone another phase of transformation into the science of genomics, which is much more global in scope and approach. Knowledge of the genomes of humans and other species as well as scientifi c advances in genome research in general will presumably help us understand the genetic instructions that make us human. From a clinical perspective, by learning about the gene sequences and the functional dynamics of the genome as well as individual genetic differences, scientists hope to understand the molecular basis of the normal state and the diseased state of life on one hand, and develop ways to individualize medicine and nutrition on the other hand. H owever, the enormous wealth of knowledge that has been accumulated through genome sequencing and genome research has created a new challenge for scientists. The new challenge is to learn how to integrate and interpret the enormous body of g enomic data to determine cause-and-effect relationships and how to predict the occurrence and progression of diseases before there are any symptoms. Parallel developments in the s cience of bioinformatics, genomic regulatory networks, and systems biology will presumably help us add meaning to the enormous body of genomic data, and in so doing will help us understand the molecular basis of biological diversity, organismal c omplexity, and life in general. Nevertheless, despite real technological progress and much journalistic hyperbole about the promise of genomics, recent advances in research have not yet radically changed the practice of medicine and nutrition. The disconnect between the hope of quick returns from advances in genomics and the reality of the long-drawn path of developing products that will improve the quality of human life may lead to under-appreciation of the progress and achievements of genomics. In this new era, the terms “genome” and “genomics” have gone beyond the boundaries of the laboratory into public life and thus we all need to know something about genomics. The current book is an attempt to present to the reader, a thorough overview of the progress of genomics to its current level.