Semiconductor Metamaterials: Part One, Volume 116 in a two-part series surveys the state-of-the-art in material platforms for optical metasurfaces. Chapters cover Metasurfaces from materials with 2nd-order nonlinearity, Light Emitting Metasurfaces based on Direct Bandgap Semiconductors, Tunable Metasurfaces enabled by Phase-Change Materials, Phase-Transition Materials for Thermal Tuning of Metasurfaces, Tunable Metasurface Devices based on Soft Matter, Infrared Metasurfaces, Polarization Sensing Platforms, UV/ Visible Metasurfaces, and Metasurfaces for Catalysis & Chemistry.