Technological development in genetics and genomics provides unprecedented possibilities to identify the underlying molecular basic of many common diseases. With the availability of the human genome sequence and growing information on the most frequent DNA variations combined with the molecular analysis on the RNA expression and protein level, diseases might be characterized in the future at the molecular level. Describing gene function anf the specific role of DNA, RNA, and proteins in the disease process provides novel diagnosis tools and treatment. Ultimately how the unique genetic signature of an individual influences the risk and prognosis of disease will be the basis for individualized medicine in the years to come.