A lens-less digital holographic microscope, a reflective digital holographic microscope, and a digital holographic microscope including a plurality of lenses. In one example, the digital holographic microscope includes a single mode fiber collimated light source which provides illumination for both the ‘science’ and ‘reference’ arms, a pair of microscope objectives located side-by side, and illuminated by the common beam, a relay lens whose center is between the two objectives, and a focal plane element where the interference pattern is measured.