According to one aspect, the invention concerns a method for microscopy of a thick sample arranged on a sample support, with edge-illumination of the sample. The method comprises, in particular, emitting at least one illumination beam (1), forming, from the illumination beam, an illumination surface, focusing the illumination surface in the sample by means of a microscope lens (120) and deflecting the illumination surface originating from the microscope lens, in order to form a transverse illumination surface, located in a plane substantially perpendicular to the optical axis of the microscope lens. The method further comprises forming, by means of said microscope lens (120), the image of an area of the sample illuminated by the transverse illumination surface on a detection surface (131) of a detection device (130), scanning the illumination beam, allowing the transverse illumination surface to move along the optical axis of the microscope lens, and superimposing the object imaging surface and the transverse illumination surface, by focusing means comprising means separate from the means for the relative axial movement of the microscope lens and the sample.