A brief review on the history of human functional near-infrared spectroscopy (fNIRS) development and fields of application

► The paper celebrates the 20th anniversary of functional fNIRS. ► Events that have shaped the present status of fNIRS are reported. ► fNIRS methodology has undergone consistent improvements over the years. ► The application of fNIRS in Medicine and basic research have been increasing. ► Technological development will augment fNIRS application in adults and infants.