The human genome project and the technological breakthroughs it has produced have moved the field of molecular medicine forward with breathtaking speed. This will impact not only the advance of scientific discoveries and the way science is conducted but also the clinical practice of medicine. In this review we explain the basic principles of these new technologies. Their potential use and impact are demonstrated by using diabetes mellitus as an example of a common and serious medical disorder. Finally, several potentially adverse consequences of "excessive" knowledge are discussed.