Ohmic loss in metal based metamaterials continues to be one of the primary impediments to their application at infrared and visible frequencies. Dielectric metamaterials offer one potential solution to this issue by eliminating ohmic loss as well as avoiding saturation in the magnetic response at high frequencies. In this talk, I will discuss our recent efforts to develop purely dielectric metamaterials at optical frequencies based on structured silicon including both non-resonant and resonant configurations. Non-resonant dielectric metamaterials are implemented for chip-based photonics using both nanostructured waveguides and adiabatically tapered waveguides. In both cases, a spatially varying refractive index profile is utilized for achieving transformation optics devices including highly efficient free-space couplers and massively parallel waveguide crossings. By avoiding resonances and metallic elements, the devices are both broadband and low-loss. I will also outline the development of resonant dielectric metamaterials for achieving near-zero refractive index at optical frequencies. These metamaterials are formed from unit cells exhibiting both electric and magnetic dipole Mie resonances. By overlapping these two resonances, we show how an impedance matched zero-refractive index can be achieved at optical frequencies. Such materials can be applied for a variety of applications including directional emitters, filters, and compact lens systems.