The overall objective of this study is to obtain data to evaluate whether high-resolution imaging of barrett's esophagus in vivo can assist clinicians in detecting dysplastic (precancerous) areas. This is a pilot study of an novel technology, a miniaturized microscope device which can be used during upper endoscopy to image the gastrointestinal epithelium. This is an exploratory, not a comparative, study designed to evaluate the feasibility of using this instrument in Barrett's esophagus.