Abstract: A scanning electron microscope useful for obtaining microscopic data or images of wet specimens is provided with comprises an electron source capable of emitting a beam of electrons; an electron optical vacuum column with means for focussing the beam of electrons; means for scanning the focussed beam of electrons across a specimen; a differentially pumped aperture column attached to the electron optical vacuum column and having at least two walls perpendicular to the sides of the differentially pumped aperture column defining a suitable series of pressure gradients, each wall having an aperture aligned to permit the beam of electrons to pass through said differentially pumped aperture column; a specimen chamber which may be maintained at normal atmospheric pressure; a specimen mount; means of preventing the buildup of negative charge on the surface of the specimen; and a detector and image recording system.