Confocal laser endomicroscopy is a newly introduced endoscopic tool that makes it possible to carry out confocal microscopic examination of the mucosal layer during ongoing endoscopy. Different types of tissue and diseases can be diagnosed immediately, facilitating early diagnosis of gastrointestinal cancer. Analysis of the in vivo microarchitecture is helpful in targeting biopsies to relevant areas. In addition, subsurface imaging can unmask microscopic diseases - (microscopic colitis) or bacterial infection ( HELICOBACTER PYLORI), for example. Molecular imaging is becoming feasible, and this will shortly open the door to new indications in gastrointestinal endoscopy (e.g., in vivo receptor analysis).