Cancer, with over 450,000 new cases diagnosed and 270,000 deaths each year, is one of the most dreaded diseases and the second most frequent cause of death in Germany. More than almost any other disease, cancer poses tremendous challenges for research and clinical practice. Practically every organ can be affected, every type of cancer has its own rules, and the underlying changes in affected cells are extremely complex. In order to develop novel, more effective methods of diagnosis and treatment, we first need to understand the basic mechanisms of cancer. In recent years, researchers at the German Cancer Research Center in Heidelberg have achieved major advances both in basic research and in the development of novel methods for clinical application. This has received special recognition in 2008, when Professor Harald zur Hausen was awarded the Nobel Prize for Medicine for his outstanding scientific contribution to the study of human papillomaviruses (HPV).