The aim of this study is to characterize the healing process of the esophageal mucosa, histologically and at the molecular level, after RFA for non-dysplastic and dysplastic Barrett's esophagus. Patients with Barrett's esophagus will undergo surveillance endoscopy with biopsy. This will be followed by RFA treatment of the BE and follow up endoscopy will be performed 1, 2, and 4 weeks after RFA. Healing at each time point will be assessed endoscopically, and molecular markers related to healing will be studied. Stem cell expression markers, immune cells and markers of epithelial-mesenchymal transition will be compared with baseline expression for each patient.