The Doctor before the first image of "Under the Skin", the Vulcan reproductive gland
"Under the Skin: Humanoid Anatomy as Art" was a twelve-part holophotographic essay created by The Doctor in 2375, exploring the aesthetics of anatomical structures.
He presented this essay aboard the USS Voyager that same year, beginning with an image of the Vulcan reproductive gland. He called attention to its composition and subtle color variations. (VOY: "Nothing Human")