Flexible endoscopy, a minimally invasive diagnostic and potentially therapeutic tool, has been more available over the past decades. A fiberscope is used to visualize the lumen of the area of interest and collect tissue or fluid samples for evaluation. Samples can be submitted for histopathology, cytologic analysis, and bacterial culture. Flexible endoscopy is being investigated. This article provides a brief review of equipment and basic flexible endoscopy followed by an overview of advanced flexible endoscopic procedures that focuses on the gastrointestinal tract. The procedures included here may become more readily available and improve diagnosis and treatment.