  Here, we present a novel microscopic technique for measuring
wavelength-dependent three-dimensional (3-D) distributions of the refractive
indices (RIs) of microscopic samples in the visible wavelengths. Employing 3-D
quantitative phase microscopy techniques with a wavelength-swept source, 3-D RI
tomograms were obtained in the range of 450 - 700 nm with a spectral resolution
of a few nanometers. The capability of the technique was demonstrated by
measuring the hyperspectral 3-D RI tomograms of polystyrene beads, human red
blood cells, and hepatocytes. The results demonstrate the potential for
label-free molecular specific 3-D tomography of biological samples.
