The ability to control flow of light is important for optical applications, leading to photonic technologies that significantly impact daily life, such as high-speed optical internet, ultrathin optical displays, novel lasers, and medical imaging tools. Over the last two decades of photonic science advances, the optical metamaterials and metasurfaces paradigm has revolutionized photonic matter design using nanoscale structures, yielding new optical properties and functions not found in natural materials. These ultrathin optical metasurfaces consist of arrays of subwavelength light scatterers (i.e., optical antennas), leading to unique control of light properties. While metasurfaces show exceptional promise, there are several limitations such as the lack of optical turnabilities of metasurfaces and the challenges on integrating functional metasurfaces into optical devices/systems, etc. In this talk, I will give an overview of our research efforts on electrically and nonlinear optically tunable meta-optics and zero-index optics for developing new active optical applications.