Confocal laser endomicroscopy (CLE) is a new diagnostic technique that allows microscopic examination of the digestive mucosa during ongoing endoscopy. Different types of tissue and diseases can be diagnosed immediately, and analysis of the in vivo microarchitecture is helpful to better target standard biopsies and reduce the number of biopsies required. CLE necessitates an intravenous injection of a fluorescent marker, e.g. fluorescein, to obtain 'optical biopsies' with a high level of magnification (up to 1000 fold). To date, more than 1000 endomicroscopy procedures have been performed in the world and different publications have shown the safety, feasibility and excellent diagnostic yield of CLE. No complication related to IV injection of fluorescein has been reported. However, all these data come from a very limited number of expert centres and need to be confirmed and validated at the multicenter level. The aims of this multicenter trial are: 1) to standardize CLE in all centres equipped in France, 2) to ensure the safety of intravenous fluorescein injection, 3) to test the diagnostic value of CLE in various conditions representative of the large spectrum of different cancerous and non-cancerous digestive diseases.