Confocal laser endomicroscopy (CLE) is a newly developed endoscopic technique. The most commonly used fluorescent substance is Fluorescein sodium.The plasma half-life of ﬂuorescein is 11 minutes. A recent test estimated that ﬂuorescein-based CLSM(confocal laser scanning microscopy) of the upper-GI tract of pigs delivers the best contrast and image quality within the ﬁrst 8 minutes after injection of ﬂuorescein .However, despite its increasing use in clinical examination,there are no data on contrast dynamics and image quality over time after injection of the ﬂuorescein sodium in the inspection of gastrointestinal tract of human being.