Method: The patients enrolled including the control group, will be investigated respectively, by conventional colonoscopy and CLE in both the terminal ileum as colon. The degree and extent of Crohn's disease are assessed by conventional ileocolonoscopy (SI), CLE (selected parameters) and histology biopsies. Terminal ileum and each colonic segment (caecum, ascending colon, transversal colon, descending colon, colon sigmoid and rectum) are assessed as described above. Then, the correlation between histology (gold standard), SI and CLE is calculated. An intra-and inter-observer study follows on CLE parameters, where 3 observers are blinded with respect to each other. The pathologist is blinded to conventional and CLE parameters. CLE results are stratified in order to identify which of the recorded CLE parameters that correlate best with the two other methods, and thus are most suitable for the characterization and activity of Crohn's disease.