The understanding of the mechanisms that explain the initiation and early evolution of colorectal cancer is evolving. This should facilitate the development of new approaches to effective prevention and intervention. Over the past years, deficiencies in the current adenoma-carcinoma model for colorectal cancer, in which APC mutation is placed at the point of initiation, have been suggested. Several pathways through which cancer may develop seem to exist, such as 'chromosomal instability' (CIN), 'microsatellite instability' (MSI), and most recently the 'serrated pathway' involving epigenetic changes. Parallel to discoveries in molecular pathways are the increased awareness of early and precursor features of the colorectal mucosa detected and treated by endoscopic and minimal-invasive techniques. Thus, new staging and classification systems have been developed to guide the clinician in diagnosis and choice of treatment. This book sets focus on selected clinical and molecular aspects of colorectal precursor lesions; from the endoscopically detected colorectal polyp, major molecular mechanisms, and aspects of protease-systems in colorectal cancer development. Future research on colorectal cancer needs to be stratified according to the appropriate clinical features and their associated genetic pathways involved in order to further explore important molecular mechanisms and clinicopathological consequences of chromosomal, microsatellite and epigenetic mechanisms.