1. A method of performing 3-D holographic microscopy of an optically trapped structure, comprising the steps of: providing an optical microscope having a focal plane; generating a laser beam having an associated imaging wavelength input to the optical microscope wherein imaging of the optically trapped structure arises from the laser beam with the associated imaging wavelength; generating from the laser beam a plurality of optical traps with wave fronts of a trapping laser beam having a phase only hologram encoding an optical trapping pattern and the trapping laser beam having an associated trapping wavelength; and providing an objective lens for the optical microscope, the objective lens both projecting the plurality of optical traps and collecting in-line holographic images of the trapped structure; and providing volumetric images of the trapped structure from the laser beam to a device for providing 3-D holographic microscopy of the trapped structure.