This textbook describes the most relevant molecular and biological processes in cancer, how they contribute to the development and progression of individual cancer types in humans, and how insights from molecular cancer research can be applied to improve cancer prevention, diagnostics and treatment. Part I of the textbook summarizes the current fundamental knowledge on the general properties of cancers, the causes of cancer, cancer genetics, genomics and epigenetics. Individual chapters address the functions of DNA damage and repair, oncogenes and tumor suppressors in carcinogenesis and discuss crucial mechanisms in cancer pathogenesis, such as apoptosis and replicative senescence, as well as the most relevant signal transduction pathways and regulatory networks. Part I concludes with a chapter on tumor invasion and metastasis and tumor immunology. In Part II, the most relevant mechanisms acting in individual human cancers (and subtypes) are described in more detail.