A lens-less holographic microscopy is developed for observation of high-resolution 4-D (spatio-temporal) images. A
complex-amplitude in-line hologram with a large numerical aperture is extracted from a large off-axis hologram by
applying one-shot digital holography. An angular spectrum method is developed for fast numerical reconstruction of
precise 3-D image from the in-line hologram with a large numerical aperture. 3-D intensity and phase images with no
distortion, with a resolution higher than 1μm, and with a depth larger than 1mm are recorded and reconstructed by the
present holographic microscopy. Possibility is demonstrated to realize 4-D measurement of microorganisms swimming in water.