Although magnifying chromoendoscopy had been a reliable diagnostic tool, narrow-band imaging (NBI) has been developed in Japan since 1999. The technology of the NBI system is based on modifying the spectral features by narrowing the bandwidth of spectral transmittance using various optical ﬁlters. To standardize these diagnostic strategies, we will focus on the NBI International Colorectal Endoscopic (NICE) classiﬁcation/ the Japan NBI Expart Team (JNET) classificationthe proposed for use by endoscopists with or without a magnifying endoscope. However, more prospective research is needed to prove that this classiﬁcation can be applied with satisfactory availability, feasibility, and reliability. In the future, NBI might contribute to the evaluation of real-time histological prediction during colonoscopy, which has substantial beneﬁts for both reducing the risk of polypectomy and saving the cost of histological evaluation by resecting and discarding diminutive adenomatous polyps (resect and discard strategy).