1. An image processing apparatus, comprising: an extraction unit configured to extract each cell region of a plurality of cells from a first image of a fundus of an eye to be inspected; a characteristic value calculation unit configured to, for each extracted cell region of the plurality of cells extracted from the first image, calculate, from a plurality of second images of the fundus, a value indicating a volume of a layer corresponding to the extracted cell region; and a display control unit configured to display, on a display unit, each extracted cell region so as to have a display status corresponding to the value indicating the volume.