Coined by Intraub and Richardson in 1989, boundary extension phenomenon refers to a visuo-spatial memory distorsion occuring when an observer tries to remember a previously perceived photograph. This distorsion results in the extrapolation of the spatial layout of the perceived scene: the observer's memory includes details that were not present in the initial scene, but likely to be found outside its limits. This article proposes to synthesize studies realized in this research area, by exposing the characteristics of the phenomenon, its limits, and theoretical points which are still open to debates.