Optical metamaterials are composed of arrays of artificial sub-wavelength structures, also known as meta-atoms, and engineered to exhibit exotic physical properties not found in nature. The design of optical meta-atoms determines their interaction with light and, at a given energy, the amplitude and polarization of transmitted, reflected, scattered, absorbed, and emitted light. Conventional fabrication methods based on e-beam and photo-lithographies and physical evaporation of materials typically restrict meta-atom designs to 2D structures, while 3D architectures require complex multi-step patterning and deposition processes. Nanoimprint lithography, combined with the deposition of bulk metals and colloidal nanocrystals with size, shape, and composition-dependent optical characteristics, enables the large-area fabrication of metamaterials from 3D meta-atom heterostructures in a single patterning step. Prototype studies have demonstrated 3D metamaterials composed of Au nanocrystals that show circular dichroism in the mid-IR. This thesis presents the fabrication and structural and spectroscopic characterization of 3D nanocrystal-based metamaterials with reconfigurable optical responses. Chemically synthesized colloidal nanocrystals are composed of inorganic cores and organic ligand shells and can be metallic, semiconducting, or dielectric materials. By juxtaposing nanocrystals on evaporated bulk thin films, chemical exchange with shorter ligands and/or thermal annealing is used to decrease the interparticle distance in nanocrystal thin films, creating misfit strain in nanocrystal/bulk metal heterostructures that drives folding to achieve 3D curvature. The introduction of phase-change VO2 nanocrystals into 3D chiral metamaterials enables thermally reconfigurable switching of mid-IR chiral responses as the VO2 traverses an insulator-to-metal transition upon mild temperature excursions. Mixing VO2 and metallic nanocrystals lowers the thermal threshold for the phase transition and tunes the energy and breadth of the chiral response. The incorporation of photoluminescent, CdSe-CdS core-shell quantum dots in 3D chiral metamaterials enables chiral luminescent responses, observable under both circularly polarized excitation and emission. Spatially resolved confocal microscopy shows the chiral selectivity is maximized along the arms and enhanced by coupling to photonic resonance modes.