Metasurfaces utilize strong interactions between light and two-dimensional nanostructured interfaces to control light at will, and enable us to break away from the reliance on light propagation by transferring an optical interface into functional devices. I will describe the effort of my research lab in creating flat optical devices that show record-breaking performance and new functionalities. These include small footprint integrated photonic devices, broadband achromatic flat lenses, metasurface holograms, and bioinspired radiative-cooling coatings.