This paper reviews recent progress in the design and fabrication of bio-inspired gradient index lenses. Inspired by the
gradient index distributions of the protein layers in biological eyes, we employ nested layers of polymer composites to
create smoothly-varying index distributions within bulk lens substrates. Because the fabrication technique allows for
independent control of the index layers, the index contours, and the final lens surfaces, optical power can be combined
with aberration control in a single element. Gradient-index singlets which correct for spherical aberration and singlets
which correct for chromatic aberration are described as examples of the utility of this class of optics.